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Session programme

CL

CL – Climate: Past, Present, Future

CL1 | PICO

This open session invites contributions in the field of ocean and land climates, which do not fit into the specialized sessions. It will welcome presentations of modelling studies as well as (paleo)-observations. Here, papers will be collected from those sessions, which attracted a too small amount of contributions and did not fit into other specialized sessions both on climatology and paleoclimatology. However this is a session by itself and you must feel free to submit directly your paper to the Open session. This guarantees all authors an appropriate representation.
Opportunities of publishing your contribution is proposed in the on-line and open access EGU journal "Climate of the Past" www.climate-of-the-past.net

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Convener: Didier Roche | Co-convener: Irka Hajdas
MAL2
Convener: Alberto Montanari
MAL7
Convener: Didier Roche
MAL14
Convener: Didier Roche
MAL22
Convener: Didier Roche

CL1 – Past Climates

GD1.1

Processes responsible for formation and development of the early Earth (> 2500Ma) are not
well understood and strongly debated, reflecting in part the poorly preserved, altered, and
incomplete nature of the geological record from this time.
In this session we encourage the presentation of new approaches and models for the development of Earth's early crust and mantle and their methods of interaction. We encourage contributions from the study of the preserved rock archive as well as geodynamic models of crustal and mantle dynamics so as to better understand the genesis and evolution of continental crust and the stabilization of cratons.
We invite abstracts from a large range of disciplines including geodynamics, geology, geochemistry, and petrology but also studies of early atmosphere, biosphere and early life relevant to this period of Earth history.

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Co-organized by AS4/CL1/GMPV3/TS14, co-sponsored by EAG
Convener: Ria Fischer | Co-conveners: Peter A. Cawood, Nicholas Gardiner, Antoine Rozel, Jeroen van Hunen
SSP4.2

Since their first colonization of terrestrial habitats more than 450 million years ago, plants have shaped the environment and climate of the Earth. As plants evolved, soils, a key interface between the geosphere and the atmosphere, also evolved. Likewise, because plants are in direct contact with the atmosphere, and are crucial for the hydrological cycle, changing environmental conditions in the Earth’s past have in turn influenced the vegetation and left an imprint on both the macrofossil and microfossil (palynological) record. In this session we aim to explore the myriad interactions between vegetation and climate during intervals of major change in deep time by bringing together palaeobotanists, palynologists, climate modellers, plant biologists and soil scientists. We intend to raise awareness for the crucial role played by plants during periods of major environmental change. This may include extinction intervals, such as the Big Five mass extinctions, oceanic anoxic events coupled to increased weathering and nutrient input, or intervals of rapid warming or cooling.

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Co-organized by CL1
Convener: Sofie Lindström | Co-conveners: Karen L. Bacon, Bas van de Schootbrugge
CL1.4

The geological record provides insight into how climate processes may operate and evolve in a high CO2 environment and the nature of the climate system during a turnover from icehouse to greenhouse state — a transition that may potentially occur in the near future. In recent years we have seen major advances in many geochemical techniques and an increase in the complexity of Earth System Models. The aim of this session is to share progress in our understanding of global changes occurring during the pre-Quaternary based on the integration of geochemical/paleobotanical/sedimentological techniques and numerical models. Specifically, we encourage submissions describing research in which both model and data approaches are embedded. We invite abstracts that reconstruct Earth’s climate from the Cambrian to the Pliocene, investigate how the interconnections of the key surface reservoirs (vegetation-ocean-atmosphere-cryosphere-biogeochemistry) impact climate, and identify tipping points and thresholds. Pertinent themes may include greenhouse-icehouse transitions and intervals testifying for extreme changes.
We are pleased to have Martin Ziegler as our invited speaker talking about "Cenozoic climate evolution revealed by clumped isotope thermometry".

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Co-organized by SSP2
Convener: Yannick Donnadieu | Co-conveners: Sietske BatenburgECSECS, Gregor Knorr, Caroline H. Lear, Bas van de Schootbrugge
SSP2.1

This session aims to showcase an interesting diversity of state-of-art advances in all aspects of Cambrian to Cretaceous paleoceanography, paleoclimatology and stratigraphy. Within this broad topic we intend to invite an exciting range of contributions including, but not limited to, organic and inorganic geochemistry, sedimentology, (micro-)paleontology, and modelling. Inter- or multidisciplinary studies are also encouraged. The session will potentially be organized into thematic blocks to allow more in-depth exploration and discussion of topics.

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Co-organized by CL1
Convener: Jens Herrle | Co-conveners: David Bajnai, Wolf Dummann
SSS12.10

Deep weathering covers, such as laterites, constitute a major expression of the critical zone, especially in tropical environments and participate significantly to the global geochemical budgets, weathering and erosion fluxes, and atmospheric greenhouse gas consumption. Despite their factual importance for the Earth surface, several important questions are still unanswered about their mode and timing of their formation, and their evolution in response to shifts in climatic and geodynamic forcing. We encourage all contributions addressing those questions using mineralogical studies, geochemical mass balance and isotopic signals in deep soil profiles or in rivers, dating tools at different time scales, or modeling approaches that can integrate those data to understand the evolution of deep weathering covers though time and their role in the global feedbacks between weathering and climate.

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Co-organized by CL1/GM3
Convener: Cecile Gautheron | Co-conveners: Julien Bouchez, Jean Braun, Emmanuelle Puceat
CR1.4

The pre-Holocene history of the Greenland Ice Sheet remains fragmentary and poorly known. The behavior and response of the Greenland Ice Sheet to past climate change, particularly during warmer-than-present times, such as the Pliocene and Pleistocene super interglacials, offer insight into the potential future response of the ice sheet to rapid anthropogenic warming. We welcome submissions that present advances in deep time records of Greenland Ice Sheet process, behavior, and history using a broad range of tools including geophysical data, geochemical and isotopic analyses, paleoecological analyses, modelling studies, and interdisciplinary data sets.

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Co-organized by CL1/GM7
Convener: Andrew ChristECSECS | Co-conveners: Paul Bierman, Dorthe Dahl-Jensen, Paul Knutz, Elizabeth Thomas
CL1.8

Orbital forcing is the most important known external driver of the climate system. Nevertheless, resultant internal climate feedbacks that invoke different climate components across different time scales play a critical role in defining the climate response to orbital forcing. These internal climate feedbacks are particularly apparent at past climate transitions, which cannot be simply explained by orbital changes alone (e.g. glacial inception and termination, the mid-Brunhes transition, the mid-Pleistocene transition, Pliocene-Pleistocene transition).

In this interdisciplinary session, we aim to bring together studies of centennial-to-orbital scale interactions among the atmosphere-ocean system, cryosphere, and carbon cycle that advance our understanding of the climate system during climate transitions. Modeling, theoretical and proxy-based studies as well as novel methodologies that combine the above approaches are especially encouraged.

Keynote talk "Ocean carbon storage and release over a glacial cycle" by Dr. James Rae, School of Earth & Environmental Sciences, University of St Andrews

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Co-organized by SSP2
Convener: Xu ZhangECSECS | Co-conveners: Steve Barker, Jesse FarmerECSECS, Gregor Knorr, Matteo WilleitECSECS
BG1.9

The solid Earth impacts the dynamics of the external spheres of the planet, altering relief, continental disposition, and geochemical cycles. In turn, the solid Earth influences the different components of climatic systems and long-term changes in biological species evolution. A range of retroactions also exist as landscape evolution and geodynamics are modulated by surface interactions and geochemical fluxes. Linking geodynamics, climate and biological evolution has experienced a recent revival due to advanced analytical techniques, but also thanks to fostered interactions between researchers from different backgrounds. These fruitful conditions shed light on interactions that could not be envisioned until recently. We gather contributions from all fields that track the interplay between solid Earth, climate and species diversification. We are interested in transdisciplinary approaches, that aim at quantifying the biotic and climatic responses to tectonics.

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Co-organized by CL1/GD1/SSP2
Convener: Laurent Husson | Co-conveners: Christine BaconECSECS, Pierre Sepulchre, Daniele Silvestro
CL1.9

The pacing of the global climate system by orbital variations is clearly demonstrated in the timing of e.g. glacial-interglacial cycles. The mechanisms that translate this forcing into geoarchives and climate changes continue to be debated. We invite submissions that explore the climate system response to orbital forcing, and that test the stability of these relationships under different climate regimes or across evolving climate states (e.g. mid Pleistocene transition, Pliocene-Pleistocene transition, Miocene vs Pliocene, and also older climate transitions). Submissions exploring proxy data and/or modelling work are welcomed, as this session aims to bring together proxy-based, theoretical and/or modelling studies focused on global and regional climate responses to astronomical forcing at different time scales in the Phanerozoic.
Dr. Qiang Fang will give an invited presentation with the title 'Astronomically paced climate changes during the demise of the penultimate icehouse'.

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Co-organized by SSP2
Convener: Christian ZeedenECSECS | Co-conveners: Anne-Christine Da Silva, Stefanie KabothECSECS, Matthias SinnesaelECSECS
CL1.10

A range of future climate scenarios are projected for higher atmospheric CO2 concentrations. The Pliocene epoch, ~5.3-2.7 Ma, has been proposed as an analogue for future climates, since it is characterised by CO2 concentrations which align with those recorded today and projected for the end of this century under moderate emissions scenarios. The Pliocene includes evidence for climate variability at orbital and sub-orbital timescales, including the development of glaciations, which offer important contrasts to the pronounced glacial-interglacial cycles of the Pleistocene. There is also the opportunity to investigate climate response to longer-term processes, including ocean gateway changes and tectonic uplift. In this session we invite contributions which examine climate variability within the Pliocene epoch at a range of scales. We welcome both data and model perspectives on ocean/atmosphere circulation, terrestrial environmental responses, ice sheets and sea-level, atmospheric CO2, biogeochemical cycling and/or ecosystem responses. We also encourage contributions linked to the PAGES-PlioVAR and PlioMIP2 programmes.

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Co-organized by SSP2
Convener: Erin McClymont | Co-conveners: Tijn BerendsECSECS, Tim Herbert, Antje Voelker
CL1.11

Heinrich stadials mark rapid reorganisations of the ocean-atmosphere system. In the Southern Hemisphere Heinrich stadials comprise distinct warming events characterised by extensive deglaciation and ocean-surface heating. In contrast, weakening of the Atlantic meridional overturning circulation during Heinrich stadials apparently cooled the North Atlantic region, if not the entire Northern Hemisphere. Our perception of Heinrich stadial climate patterns informs much of our understanding of past climate dynamics and sustains palaeoclimate paradigms such as the bi-polar seesaw. Yet emerging data from both marine and terrestrial proxies hint at boreal warmth during Heinrich stadials, suggesting that these events may in fact mark periods of amplified Northern Hemisphere seasonality rather than sustained, year-round cold. Resolving the global expression of Heinrich stadials therefore has direct implications for our understanding of Earth’s climate, past, present, and future. This session brings together the latest terrestrial and marine data in order to review our understanding of Heinrich stadials as abrupt climate change events: how they are manifested, the dynamics involved, and how these signals propagate across the ocean-atmosphere system. Our emphasis is on the most recent stadial events (i.e., HS0–HS3), for which data are generally most abundant, but we stress the temporal and geographic scope of this session is broad. We aim to foster discussion on the causes and impacts of Heinrich stadials at all latitudes, and to assess the implications of Heinrich stadials within the context of past and future climate regimes.

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Convener: Gordon Bromley | Co-conveners: Steve Barker, Margaret JacksonECSECS, Samuel Toucanne
CL1.12

Abrupt climate change is a recurring feature of the Earth’s history and the current anthropogenic interference has set the climate system on a potential abrupt change trajectory. As with past climate change, future climate changes are not predicted to affect all areas of the planet in the same way, or at the same rate, yet mechanisms for spatiotemporal differences are complex and difficult to predict from low-resolution global models.
Increasingly detailed high temporal resolution proxy reconstructions of past abrupt climate transitions and oscillations (such as the Late Glacial-Holocene transition, or the Dansgaard-Oeschger cycles) have been produced for widely distributed ice core, marine and terrestrial records. When precisely integrated (i.e. via cosmogenic isotopes, palaeomagnetic excursions, tephra) these now allow for an integrated assessment of the anatomy, the spatially variable consequences and the mechanisms of abrupt climate transitions.
With a focus on the period from the last interglacial to the pre-Industrial, this session will assess methodologies (numerical and/or proxy based) and findings from studies of the spatiotemporal anatomy of the climate system on decadal to millennial timescales. We invite contributions that evidence regional climate thresholds and gradients, explore their consequences for human societies and identify mechanisms from the integration of local to global proxy records as well as modelling approaches. Finally, we explore how findings from such precisely integrated records in space and time can serve to quantify vulnerabilities and regional thresholds relevant for the anthropogenic climate change trajectory.

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Convener: Dirk Sachse | Co-conveners: Simon Blockley, Christine Lane, Ina NeugebauerECSECS, Felix Riede
CL1.13

The carbon cycle and climate are tightly linked over millennia and centennial time scale, as is exemplified by the synchronous changes between CO2 and Antarctic temperature recorded in ice cores. Aside from CO2, other data such as carbon isotopes also show strong changes in the carbon cycle between the colder Last Glacial Maximum and warmer pre-industrial. However, despite decades of research with data and climate models, no complete explanation has emerged to account for all data records. We invite contributions from both proxy data and models tackling these issues and bringing new insights on the carbon cycle changes during the Last Glacial Maximum and last deglaciation. In particular, we welcome contributions from models of all complexities from simple theoretical models to complex GCMs, as well as new records or interpretation of proxy data from ice and sediment cores, spanning centennial to millennial time scales and involving ocean or land processes.
Our invited speaker will be Alice Marzocchi talking about "Global cooling linked to increased glacial carbon storage via changes in Antarctic sea ice".

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Convener: Nathaelle Bouttes | Co-conveners: Ruza IvanovicECSECS, C. Waelbroeck, Christoph Nehrbass-Ahles, Bernhard Bereiter
CL1.14

Ice cores are a key archive to study past climate variability. Various physico-chemical proxies provide key insights into past temperature, atmospheric composition, volcanic activity, and atmospheric circulation. Despite the large body of empirical information available, we still lack a detailed, process-based understanding of the creation of the archived climatic signal. This session aims, in light of the new "Beyond EPICA Oldest Ice" (BE-OI) ice-core project, at an in-depth discussion on the extent to which climatic signals are archived in the proxy signals, how the archival processes – from the atmosphere to the surface to post-depositional changes in the firn and ice and even further smoothing/diffusion in the lower most part of the ice column – themselves affect the recorded signal, and how to optimally recover the original signals from existing ice-core records.
We welcome contributions that shed light on this chain of processes, including interpretation of various proxies from new, or existing, ice core records from Antarctica, Greenland or high mountainous areas; analyses of climate model, reanalysis and back trajectory data; novel application of statistical and spectral methods to proxy data; or new measurement techniques. Finally, we encourage discussion about the impact the individual processes have on the relationship between proxy and past climate variability across various temporal and spatial scales.

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Co-organized by CR2
Convener: Mathieu CasadoECSECS | Co-conveners: Pete AkersECSECS, Marie CavitteECSECS, Thomas MünchECSECS
SSP2.2

Earth history is punctuated by major extinction events, by perturbations of global biogeochemical cycles and by rapid climate shifts. Investigation of these events in Earth history is based on accurate and integrated stratigraphy. This session will bring together specialists in litho-, bio-, chemo-, magneto-, cyclo-, sequence-, and chronostratigraphy with paleontologists, paleoclimatologists and paleoceanographers. An emphasis is placed upon the use of a variety of tools for deciphering sedimentary records and their stratigraphy across intervals of major environmental change. This session is organized by the International Subcommission on Stratigraphic Classification (ISSC) of the International Commission on Stratigraphy (ICS) and it is open to the Earth science community at large.

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Co-organized by CL1, co-sponsored by ICS and ISSC
Convener: David De VleeschouwerECSECS | Co-conveners: Frederik Hilgen, Werner Piller, Tiffany Rivera, Christian ZeedenECSECS
CL1.16

Significant advances in our understanding of the development of Cenozoic polar continental margins have been made over the last two decades by studying continental shelf and slope sediment sequences. These include more detailed reconstructions of the climatic, oceanographic, and tectonic evolution of high northern and southern latitudes over various time scales, as well as reconstructions of past ice-sheet dynamics and studies of marine geohazards. Data have been obtained from conventional and high-resolution 2D and 3D seismic surveying, as well as from a growing number of short sediment cores and targeted high-latitude deep drilling expeditions (e.g. IODP, MeBO). The same techniques have also been applied in fjords, which link the continental margins with the interiors of landmasses and act as “miniature ocean basins”. Fjord settings allow us to study similar geological processes to those that acted on glaciated continental margins but at smaller scales. The variety of sediment inputs (e.g. glacial, fluvioglacial, fluvial, biological) to fjord basins along with relatively high sedimentation rates provides the potential for high-resolution palaeoclimatic and palaeooceanographic records on decadal to centennial timescales.

The aim of this session is to bring together researchers working on both northern and southern high latitudes processes spanning various spatio-temporal scales from continental margins to fjords, to provide a multi-disciplinary picture of polar areas. We welcome submissions focussing on (but not limited to) records of past climatic change, tectonics, oceanography and ecosystems, and the associated links with ice sheets and glacier behaviour, ice-ocean interactions and glacial-marine sedimentary processes. Studies that integrate different datasets, data types, or that marry observations with numerical modelling are also encouraged.

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Co-organized by OS1/SSP3
Convener: Johann Philipp KlagesECSECS | Co-conveners: Florence Colleoni, H. Christian Hass, Kelly Hogan, Michele Rebesco
CL1.17

Over the last decade, PaleoMex - Paleo Mediterranean eXperiment (MISTRALS)- has been promoting interdisciplinary research between natural and social sciences to improve our understanding of the Mediterranean climate and provide background environmental information to human societies evolution over the Holocene. Abrupt climate changes such as the Little Ice Age, the Medieval Optimum, or the 8.2 and 4.2 events represent temporal targets to explore the consequences of temperature and precipitation changes on ecosystems and human societies. This session encourages contributions based on proxy reconstructions of past environmental changes, dual model-data approaches, or new statistical tools enlightening climate variability and bringing new knowledge on the interactions between climate, environment with human societies.

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Convener: Nathalie Combourieu-Nebout | Co-conveners: Mehdi Saqalli, Marie-Alexandrine Sicre
CL1.18

This session aims to place recently observed climate change in a long-term perspective by highlighting the importance of paleoclimate research spanning the past 2000 years.
We invite presentations that provide insights into past climate variability, over decadal to millennial timescales, from different paleoclimate archives (ice cores, marine sediments, terrestrial records, historical archives and more). In particular, we are focussing on quantitative temperature and hydroclimate reconstructions, and reconstructions of large-scale modes of climate variability from local to global scales.This session also encourages presentations on the attribution of past climate variability to external drivers or internal climate processes, data syntheses, model-data comparison exercises, proxy system modelling, and novel approaches to producing multi-proxy climate field reconstructions.

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Convener: Sarah S. EgglestonECSECS | Co-conveners: Stella AlexandroffECSECS, Hugo Beltrami, Oliver Bothe, Andrea Seim
ITS2.3/CL1.19

The Ancient Silk Road was one of the most important passages for trans-Eurasia exchange and human migration, which witnessed the rise and fall of ancient civilizations in Central Eurasia. In the central part of the Ancient Silk Road, where the climate condition is extremely dry and the ecosystem is very fragile. The climate and environment changes, especially the water resources change in this area, can significantly influence the spatio-temporal distribution of Ancient Silk Road network, the trans-Eurasia exchange and human migration along the Ancient Silk Road, and the civilization evolution of these ancient cities and towns among the Ancient Silk Road network. This session aims to explore the history of trans-Eurasia exchange, human migration, Ancient Silk Road network spatial change, civilization evolution and climate and environment change, as well as relationship among them in the areas along the Ancient Silk Road. We welcome presentations concerning these issues from multi-disciplinary perspectives, to promote the advancements of research in the field.

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Co-organized by GM10/SSP1
Convener: Juzhi Hou | Co-conveners: Jianhui Chen, Guanghui Dong, Xiaoyan Yang, Haichao XieECSECS
CL1.20

While the information, preserved in the records of instrumental measurements, provide an inside view into the history of weather-related extremes of the last 100-150 years or shorter, documentary evidence and the results of natural scientific investigations allow to extend this knowledge several centuries (or millennia) into the past. This concerns, for example those disastrous extremes which were not recorded in the instrumental period, but are known from documentary sources. Compared to palaeo-hydrological investigations of extremes, the papers presented in this session are aimed to provide high-resolution information (with exact dating) based on data derived from documentary evidence, covering a period that does not exceed one-two millennia.
On the one hand, investigations focused on the long-term understanding of variability, changes and shifts in the climatic and/or hydrological regime as well as in the frequency/magnitude of meteorological and hydrological extremes and hazards are welcome. On the other hand, investigations concentrating on one or more great extreme events (extreme cold, heat, floods, droughts etc.) are also invited in the session. Papers discussing the detection of causes of hydrological, meteorological extremes and hazards (environmental, atmospheric/climatic and society-related) in historical times are also addressed and supported to participate in the session. Thus, another important topic of the session is socio-economic responses on extremes or catastrophic events as well as long-term changes, development in cooping weather-related natural hazards. As an integrate part of socio-economic response, the perception and social representation of weather and hydrological hazards and extremes (e.g. floods, droughts) in historical periods are also valuable topics of discussion in the session.
Since this research requires the development of regional chronologies based on good-quality historical sources, besides natural and applied scientists, the active presence and work of historians is of vital importance. The results of historical hydrology investigations and the study of hydro-meteorological extremes in historical times may be utilised in a number of areas such as risk assessment, flood control, hydrological forecasting/predictions, socio-hydrology or in the understanding of the main drivers of hydro-morphological processes.

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Co-organized by HS13
Convener: Andrea Kiss | Co-conveners: Rudolf Brazdil, Mariano Barriendos, Günter Blöschl
GD7.2

Interdisciplinary study of the Northeast Atlantic region offers an extraordinary opportunity to advance understanding of interactions and co-dependencies between the solid Earth, ocean, atmosphere, cryosphere and climate. Understanding these issues are of critical importance to Europe and Scandinavia, and they are of global relevance. The unprecedented surge in exploration of the Northeast Atlantic Realm that has unfolded in recent years has delivered major leaps forward in understanding its geological structure, dynamics and development, economic resources and volcanism. Examples include the complexity of the conjugate volcanic rifted margins, contact metamorphism of carbon-rich shales by sill intrusions, producing thermogenic methane, the discovery of widespread continental crust in the ocean, the critical role of the Greenland-Iceland-Faroe bathymetric ridge in influencing ocean circulation between the Arctic and the Atlantic south of Iceland, mapping of gas hydrates and the study of crustal structure beneath the Greenland icecap. Throughout the Cenozoic these factors have influenced ocean and atmosphere composition and circulation, climate change, and the growth, wastage and transport of ice. Detailed understanding of the interdependencies of these phenomena in the past and through time is arguably of critical importance to understanding the current, rapid changes in the natural environment. The goal of this special session is to bring together diverse contributions drawing on all the above disciplines in order to identify potentially fertile areas for broad, cross-disciplinary study of the Northeast Atlantic Realm moving forward.

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Co-organized by CL1/OS1/TS6
Convener: Laurent Geoffroy | Co-conveners: G.R. Foulger, Dieter Franke, Catherine Kissel
CL1.22

Palaeoenvironmental records and climate models are two contrasting and yet complementary sources of information on past climates. Both approaches independently generate insights into the dynamics of the climate system. However, more information can be extracted about the drivers of climate variability and change when the two approaches are combined. Climate reconstructions can be used to constrain and evaluate model simulations, while climate models can be used to explore the mechanisms that have driven past climatic changes. Palaeoclimate data–model comparisons can also be used to assess model performance, to constrain projections of future climate change, or to study the drivers of climate variability and change.

Here we invite contributions that integrate data from observational sources and climate models; data-model comparisons (including isotope enabled models or local calibration studies); studies that use data records to evaluate climate models or studies that use climate model outputs to understand the physical controls of climate variability.

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Convener: Laia Comas-BruECSECS | Co-conveners: Sandy Harrison, Kira Rehfeld
CL1.23

In recent decades, quantitative methods have become increasingly important in the field of palaeoenvironmental, palaeoclimatic and palaeohydrological reconstruction, due to the need for comparison between different records and to provide boundary conditions for computational modelling. Continental environmental archives (e.g. speleothems, lake sediments, land snails, rivers, or peatlands) are often highly temporally resolved (subdecadal to seasonal) and may provide more direct information about atmospheric and hydrological processes than marine archives. The wide variety of archive types available on land also allows for intercomparison and ground-truthing of results from different techniques and proxies, and multi-proxy reconstructions from the same archive can disentangle local and supra-regional environmental conditions. This approach is particularly useful for the reconstruction of hydrological dynamics, which are challenging to reconstruct due to their high spatial variability, signal buffering, nonlinearities and uncertainties in the response of palaeoclimate archives and proxies. For example, climate-independent factors such as land cover change can affect the local to regional water availability recorded in proxies.

This session aims to highlight recent advances in the use of innovative and quantitative proxies to reconstruct past environmental change on land. We present studies of various continental archives, including but not limited to carbonates (caves, palaeosols, snails), sediments (lakes, peats, rivers, alluvial fans), and biological proxies (tree rings, fossil assemblages, biomarkers). We particularly include studies involving the calibration of physical and chemical proxies that incorporate modern transfer functions, forward modeling and/or geochemical modeling to predict proxy signals, and quantitative estimates of past temperature and palaeohydrological dynamics. We also include reconstructions of temperature and hydrologic variability over large spatial scales and palaeoclimate data assimilation. This session will provide a forum for discussing recent innovations and future directions in the development of terrestrial palaeoenvironmental proxies on seasonal to multi-millennial timescales.

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Convener: Sebastian F.M. Breitenbach | Co-conveners: Ola Kwiecien, Jessica Oster, Elli RonayECSECS
CL1.24

Tree rings are one of nature’s most versatile archives, providing insight into past environmental conditions at annual and intra-annual resolution and from local to global scales. Besides being valued proxies for historical climate, tree rings are also important indicators of plant physiological responses to changing environments and of long-term ecological processes. In this broad context we welcome contributions using one or more of the following approaches to either study the impact of environmental change on the growth and physiology of trees and forest ecosystems, or to assess and reconstruct past environmental change: (i) traditional dendrochronological methods including studies based on tree-ring width and density, (ii) stable isotopes in tree rings and related plant compounds, (iii) dendrochemistry, (iv) quantitative wood anatomy, (v) ecophysiological data analyses, and (vi) mechanistic modelling, all across temporal and spatial scales.

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Convener: Kerstin Treydte | Co-conveners: Flurin Babst, Giovanna Battipaglia, Jan Esper
SC2.11

In an era of science that uses numerical models to better understand physical processes occurring on Earth, there is an increasing demand for robust empirical datasets to constrain these simulations. Generating robust datasets, especially data sets that express stratigraphic positions of sedimentary deposits as ages, often involves the use of multiple, independent geochronological techniques (e.g. different kinds of radioisotopic dating, magneto-, bio-, cyclostratigraphy and sedimentologic relationships along the succesion). The integration of these different kinds of geochronological information often poses challenges.

Age-depth models are the ultimate result of the integration of different geochronological techniques, and range from linear interpolation to more complex Bayesian techniques. We will introduce several modelling concepts and their application in a range of paleoenvironmental and paleoclimatic records. The Short Course will provide an introduction to the field of (Bayesian) age-depth models and will highlight the assumptions, benefits and limitations of different model approaches. It will prepare participants for independent application of suitable age-depth models to their data.

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Co-organized by CL1/GM14/SSP5
Convener: Christian ZeedenECSECS | Co-convener: David De VleeschouwerECSECS
CL1.26

Speleothems and continental carbonates (e.g. travertines, anthropogenic travertines, subglacial and cryogenic carbonates) are important continental archives, which can provide precisely dated, high-resolution records of past environmental and climate changes across all climate zones. This session aims to showcase the most recent developments and findings related to analytical developments, process understanding, and new records on annual, seasonal, sub- and orbital timescales. In this session, contributions are particularly welcome on: (1) monitoring of soil and cave systems in order to improve understanding of the speleothem and continental carbonate archive; (2) high-resolution orbital and sub-orbital palaeoclimate reconstructions on Quaternary timescales and longer; (3) new and novel techniques as well as methodological developments as applied to speleothems and continental carbonates; (4) interdisciplinary approaches that combine speleothem and/or continental carbonate records with other proxy archives and/or modelling.

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Co-organized by GM13
Convener: Gina E. Moseley | Co-conveners: Andrea Borsato, Jens Fohlmeister, Gabriella KoltaiECSECS, Franziska LechleitnerECSECS
CL1.27

Inspired by the classic textbook “Tracers in the Sea” (Broecker and Peng, 1982) for the session’s name, we invite contributions bearing on chemical and isotopic tracers used in paleoceanography. Proxies are the backbone of paleoceanography and undergo frequent new developments. New analytical techniques and applications allow for the investigation of new proxy systems as well as the exploration of existing proxies with new substrates or more challenging sample sizes. Growing datasets have led, and are leading, to comprehensive compilations, proxy inter-comparisons, and quantitative tests of paleoceanographic model simulations. For this session, we invite presentations on both (i) modern calibrations and downcore applications, (ii) single and multiple proxies, and (iii) proxy measurements and modeling. Despite their wide applications, paleoceanographic proxies suffer generally from significant limitations. As illustrated in a famous figure by the late H. Elderfield, our confidence in a proxy goes from an optimism phase, to a pessimism phase, and eventually to a realism phase. In this spirit, both “good” and “bad” news during the development and application of proxies are welcome.

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Convener: Ning ZhaoECSECS | Co-conveners: Olivier Marchal, Janne RepschlaegerECSECS
CR2.3

Formerly-glaciated areas are vital environments for understanding the rates of and processes of ice-mass retreat, providing analogues for improving our understanding of present-day ice masses and their response to recent and future climatic warming. Geological and geophysical records of formerly-glaciated margins on continental shelves and within large marine basins provide a wealth of landform, sediment and stratigraphic assemblages that reveal ice sheet flow and retreat dynamics over glacial-interglacial cycles. Most of the ice-sheets that produced these continental shelf archives were marine-based, grounded below sea level. These are some of the most dynamic and sensitive parts of the modern cryosphere, and are also amongst the hardest to predict the behaviour of, producing large uncertainties in predictions of future ice-sheet change in response to oceanic and atmospheric forcing.
The proliferation of geophysical technology and datasets, such as multibeam echosounder, high-resolution, 2D and 3D seismic and subsurface profiling, core logging coupled to sedimentology and palaeoenvironmental analyses, enable us to access sedimentological, stratigraphic and morphological archives of ice-ocean-sedimentary systems on formerly-glaciated continental shelves.
We invite papers on themes including past ice-flow dynamics in marine-based ice sheets, grounding line behaviour, palaeo-ice stream, shear margin and subglacial processes, the role of meltwater on glaciological systems, and on ice-ocean interactions, including ice shelf behaviour, as well as submerged archives from rarely occurring terrestrially-terminating ice sheets. Additionally, we strongly encourage contributions that develop and integrate multiple data types, and that couple geological and geophysical methods with numerical modelling of ice sheets.

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Co-organized by CL1/GM7
Convener: Andy EmeryECSECS | Co-conveners: Jeremy ElyECSECS, Mariana EstevesECSECS, Kelly Hogan, Stephen McCarron
CL1.29

Polar regions are particularly sensitive to climate variability and play a key role in global climate through various feedback mechanisms. To more fully understand the role of polar regions on global climate, a long time perspective is needed. In this session we invite contributions dealing with all aspects of Phanerozoic (i.e. Cambrian to Holocene) geology from high latitude regions: stratigraphy, paleoclimate, and modelling.

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Co-organized by SSP2
Convener: Kasia K. SliwinskaECSECS | Co-conveners: Jennifer M. Galloway, Madeleine VickersECSECS
CL1.30

The water cycle is fundamental for life on Earth, but difficult to reconstruct directly for the past without detailed instrumental records. Assessing future regional hydrological changes requires a good understanding of different components of the water cycle in a landscape (e.g. glaciers, lakes, rivers, peatlands, vegetation) and how they have developed in the past.
However, hydrological dynamics are more challenging to reconstruct than temperatures due to their high spatial variability, signal buffering, nonlinearities and uncertainties in the response of available paleoclimate archives and proxies. Furthermore, not all hydrological responses are climatically-driven. A specific archive or hydrological proxy could indicate hydrological shifts also when vegetation changes successively or when humans alter drainage systems or land cover.
To assess the state-of-the-art and the limits of knowledge on paleohydrological reconstructions, we welcome integrative contributions that address the past response of hydrological systems to local, regional and global environmental change and that discuss uncertainties and knowledge gaps in paleohydrological reconstructions, including, but not limited to:
• hydro-proxy development
• integrative syntheses of hydro-proxy information from several sites
• multi-archive and/or multi-(hydro-)proxy approaches from a single site
• statistical approaches to assess uncertainties in hydrological proxy responses
• regional to global paleohydrological modelling
• dependencies of hydrological variables: a) with other climate variables in the past (e.g. covariation of temperature and precipitation) and/or b) with non-climatic factors (e.g. land cover change, human impact)
Any paleoclimatic approach that studies (parts of) the terrestrial water cycle in the widest sense (lake and peatland water budgets, water isotopes, hydroclimate from tree rings, past fire regimes, land cover and precipitation modelling etc.) can be presented in the session. We also invite scientists working in modern experimental and observational projects that might be an important reference to calibrate and interpret palaeohydrological records.

Vivi Vajda, Swedish Museum of Natural History, will provide a comprehensive deep time perspective on past hydrological changes.

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Co-organized by HS13
Convener: Elisabeth DietzeECSECS | Co-conveners: Mariusz Lamentowicz, Joshua Larsen, Michał Słowiński
SSP2.3

A review of the progress being made towards isolating the eustatic signal from the sedimentary record, with a particular emphasis on pre-Pleistocene stratigraphy. Is a consensus emerging on the timing, magnitude and drivers of eustasy, and what are the tools that we can use to make valid assessments?

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Co-organized by CL1
Convener: Mike Simmons | Co-conveners: Ken Miller, David Ray, Frans van Buchem
SSS3.4

Palaeosols represent valuable records of the local to regional combinations of environmental factors that were present during the time of their formation. Significant progress in deciphering these records has been achieved e.g. through advances in analytical methods, such as in the fields of isotopic techniques, plant-derived biomarkers, geochemical weathering indices, microscopic and sub-microscopic techniques.
In this session we particularly welcome contributions on:
(1) the use of palaeosols as records of local to regional present and former environments,
(2) advances in biochemical, geochemical, (sub-)microscopic and other techniques in palaeopedology,
(3) experiments and basic research, aiming at improving the interpretation of palaeoenvironmental data such as biomarker and isotope data,
(4) predictions of future soil changes as a result of changes in environmental conditions and/or land-use, based on observed past soil responses to environmental changes.

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Co-organized by CL1/SSP1
Convener: Florian HirschECSECS | Co-convener: Tobias SprafkeECSECS
ITS2.1/GM12.4

Organised by the Joint IGU-IAG Commission/Working Group on Geomorphology and Society: Past, Present, and Future, this session aims to discuss the dualism of the relationship between geomorphological processes and people, and how this has developed over time.
This session is targeted at providing a platform for scientists with common interests in geomorphology and, in particular, the complex and integrated nature of the relationship between landforms, geomorphological processes and societies. As such, we are inviting contributions that focus on the two-way interactions between geomorphological processes/landforms and human activity. These should show how the various factors of the physical environment interact with the anthroposphere, and, in turn, how population and individuals may affect (and change) these factors. As a corollary, contributions may center on interrelationships between man and the landscape, or human-landscape relations, with mutual interaction.
In this context, topics of different fields may be addressed in the session such as landform evolution, landscape sensitivity and resilience in the overall context of the interrelation between geomorphology and society, geohazards, geoheritage and conservation, geomorphological responses to (and evidence for) environmental change, and applied geomorphology.
Possible key concepts may include the concept of space and the concept of time, which involves the paradigms of dynamical systems, nonlinearities, chaotic behaviour and even panarchy in geomorphological and social systems, including cultural landscapes and landscape conservation and heritage. Moreover, issues of scale and hierarchies may be addressed, and methods and applications of dynamic rather than equilibrium ideas and metaphors.
Contributions should provide new insights how to conceptualize, analyse, model and/or interpret such two-way interactions between geomorphological processes/landforms and human activity in the past, present or future. While case studies are welcome to underpin the overall string of arguments, they should be framed by and embedded in methodological approaches and concepts to enable transferability and further scientific discussion.

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Co-organized by CL1/NH9/SSP1
Convener: Margreth Keiler | Co-conveners: Sanja Faivre, Sven Fuchs
SSP1.5

Carbonate (bio)minerals play an essential role in shaping our understanding of the evolution of life and the Earth System, and constitute one of the most important archives of past climatic and environmental conditions. Geochemical, petrographic or crystallographic approaches have yielded new insights into the physico-chemical conditions governing their formation, including through biomineralisation pathways. These capture vital information about the environment and fluid chemistry during precipitation in the form of their specific elemental or isotopic signatures, mineralogies or micromorphologies. Over the past decades, a refined understanding of both biogenic as well as abiotic carbonate archives, together with the development of new analytical methods and palaeo-proxies, has led to numerous breakthroughs in palaeoclimate research. However, the quality and reliability of the climatic and environmental information we extract from these records depends, critically, on careful proxy calibrations and the evaluation of secondary controls such as kinetic or vital effects and diagenetic influences. This session seeks contributions from sedimentology, geochemistry and (palaeo)biology that utilise carbonate (bio)minerals to improve our understanding of past environmental conditions over a broad range of timescales, including (but not limited to) microbialites, mollusc shells, coral skeletons or foraminifera. We welcome experimental or theoretical studies dealing with culturing of calcifying organisms, synthetic carbonate precipitation, transformation or alteration processes, elemental partitioning or isotopic fractionation (to give but a few examples). The aim of this session is to synthesize recent progress on the investigation as well as application of these important archives, and to showcase methodological advances that will help us to build a more comprehensive understanding of past global changes.

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Co-organized by BG1/CL1
Convener: Niels de WinterECSECS | Co-conveners: Michael HenehanECSECS, Hana JurikovaECSECS, Johan VellekoopECSECS, Sebastian ViehmannECSECS
SSP2.13

Interactions between tectonics, climate and biotic evolution are ideally expressed in Asian orogenies. The ongoing surge of international research on Asian regions enables to better constrain paleoenvironmental changes and biotic evolutions as well as their potential driving mechanisms such as global climate, the India-Asia collision and the tectonic growth of the Himalayan-Tibetan and other Asian orogens. Together these efforts allow for a comprehensive paleogeographic and paleoenvironmental reconstructions that enable to constrain climate modelling experiments which permit validation of hypotheses on potential interactions.
The goal of this session is to assemble research efforts that constrain Asian tectonic, climate (monsoons, westerlies, aridification), land-sea distribution, surface processes or paleobiogeographic evolution at various timescales. We invite contributions from any discipline aiming for this goal including broadly integrated stratigraphy, tectonic, biogeology, climate modelling, geodynamic, oceanography, geochemistry or petrology.

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Co-organized by CL1/EMRP3/GD7/TS7
Convener: Guillaume Dupont-Nivet | Co-conveners: Frederic Fluteau, Carina Hoorn, Niels MeijerECSECS, Douwe J. J. van Hinsbergen
SSP2.8

Today the Indo-Pacific Warm Pool (IPWP) represents a crucial part of the global thermohaline circulation by acting as a low latitude heat source for the polar regions. The IPWP’s importance in deciphering past and future coupled ocean-atmosphere dynamics is highlighted by the complex interactions between this region and globally significant climatic systems like the Australasian Monsoon, Intertropical Convergence Zone (ITCZ), El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD).

This session will explore the IPWP’s role in global climate change and its emergence as a biogeographic diversity hot spot from the geological past to the present. We invite submissions on a broad range of topics in sedimentology, palaeontology, paleoclimatology/-oceanography, and data-model comparisons to assemble a comprehensive view of the Cenozoic evolution of the entire Indo-Pacific Region. We encourage submissions stratigraphically synthesising marine-terrestrial multi-proxy archives, and those investigating teleconnections between the IPWP, zonal (ENSO/IOD), and high latitude processes. Finally, this session will examine how the long-term evolution of the global monsoons and the ITCZ affected feedbacks between IPWP, Australasian hydroclimate and tectonic/weathering processes.

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Co-organized by CL1/OS1
Convener: Gerald AuerECSECS | Co-conveners: Anna Joy DruryECSECS, Or BialikECSECS, Kate Littler, Mathias Harzhauser

CL2 – Present Climate

CL2.1

The radiation budget of the Earth is a key determinant for the genesis and evolution of climate on our planet and provides the primary energy source for life. Anthropogenic interference with climate occurs first of all through a perturbation of the Earth radiation balance. We invite observational and modelling papers on all aspects of radiation in the climate system. A specific aim of this session is to bring together newly available information on the spatial and temporal variation of radiative and energy fluxes at the surface, within the atmosphere and at the top of atmosphere. This information may be obtained from direct measurements, satellite-derived products, climate modelling as well as process studies. Scales considered may range from local radiation and energy balance studies to continental and global scales. In addition, related studies on the spatial and temporal variation of cloud properties, albedo, water vapour and aerosols, which are essential for our understanding of radiative forcings and their relation to climate change, are encouraged. Studies focusing on the impact of radiative forcings on the various components of the climate system, such as on the hydrological cycle, on the cryosphere or on the biosphere and related carbon cycle, are also much appreciated. This session will include a dedicated section with the aim to move towards an harmonization of ground measurements of the surface radiation budget over land and ocean, with particular attention to the definition of best practices, uncertainties and traceability to standards.

Invited Speaker: Robert Weller (Woods Hole Oceanographic Institution, Massachusetts, USA)

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Co-organized by AS4
Convener: Martin Wild | Co-conveners: Paul Stackhouse, Jörg Trentmann
CL2.2

The fundamental signature of a changing climate is the departure from a global mean energetic steady state condition. The overall response of the climate system is the result of a complex interplay of multiple forcings and feedbacks with diverse spatial patterns.
In this session, we want to focus on the mechanisms through which the spatial distribution of planetary energy at the TOA, the surface, and within the atmosphere determine the meridional flows of heat and moisture from the tropics to the poles. These energy transports are tightly intertwined with the large-scale atmospheric and oceanic circulations and the hydrological cycle. Examples are the modulation of the Hadley circulation, ITCZ and monsoon dynamics, as well as Rossby waves that affect the incidence of precipitation and regional climate.
We invite submissions addressing the interplay between Earths’ energy budget (ERB), associated energy exchanges, and the response of the general circulation using modeling approaches, theoretical considerations, and observations. Submissions on the implications of such changes for polar climate and extreme weather are also encouraged. We further solicit studies on the forcings, feedbacks and mechanisms that determine spatial patterns in ERB and their implications.

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Co-organized by AS4
Convener: Maria Z. HakubaECSECS | Co-conveners: Valerio LemboECSECS, Norman Loeb
CL2.3

Changes in seasonal timing affect species and ecosystem response to environmental change. Observations of plant and animal phenology as well as remote sensing and modeling studies document complex interactions and raise many open questions.

We invite contributions with cross-disciplinary perspectives that address seasonality changes based on recent plant and animal phenological observations, pollen monitoring, historical documentary sources, or seasonality measurements using climate data, remote sensing, flux measurements or modeling studies. Contributions across all spatial and temporal scales are welcome that compare and integrate seasonality changes, study effects of long-term climate change or single extreme events, emphasize applications and phenology informed decision-making, discuss species interactions and decoupling, advance our understanding of how seasonality change affects carbon budgets and atmosphere/biosphere feedbacks, and integrate phenology into Earth System Models.

We emphasize phenology informed applications for decision-making and environmental assessment, public health, agriculture and forest management, mechanistic understanding of the phenological processes, and effects of changing phenology on biomass production and carbon budgets. We also welcome contributions addressing international collaboration and program-building initiatives including citizen science networks and data analyses.

This session is organized by a consortium representing the International Society of Biometeorology (Phenology Commission), the Pan-European Phenology Network - PEP 725, the Swiss Academy of Science SCNAT, the TEMPO French Phenology Network and the USA National Phenology Network.

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Convener: Iñaki Garcia de Cortazar-Atauri | Co-conveners: Marie Keatley, Christina Koppe, Helfried Scheifinger, Yann Vitasse
CL2.4 | PICO

Large-scale atmospheric circulation dynamics are the major driver of near surface climatic and environmental variability. Synoptic climatology examines atmospheric circulation dynamics and their relationship with near surface environmental variables. Within synoptic climatological analyses, a wide variety of methods is utilized to characterize atmospheric circulation (e.g., circulation and weather type classification, regime analysis, teleconnection indices). Various linear and non-linear approaches (e.g., multiple regression, canonical correlation, neural networks) are applied to relate the circulation dynamics to diverse climatic and environmental elements (e.g., air temperature, air pollution, floods).

The session welcomes contributions from the whole field of synoptic climatology. This includes application studies for varying regions, time periods (past, present, future) and target variables and in particular contributions on the development and the comparison of methods (e.g., varying circulation type classifications) and conceptual approaches (e.g., circulation types versus circulation regimes).

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Co-organized by AS5
Convener: Christoph Beck | Co-conveners: Andreas Philipp, Pedro M. SousaECSECS, Jan StryhalECSECS
CL2.5

As the most evident example of land use and land cover change, urban areas play a fundamental role in local to large-scale planetary processes, via modification of heat, moisture, and chemical budgets. With rapid urbanization ramping up globally it is essential to recognize the consequences of landscape conversion to the built environment. Given the capability of cities to serve as first responders to global change, considerable efforts are currently being dedicated across many cities to monitor and understand urban atmospheric dynamics and examine various adaptation and mitigation strategies aimed to offset impacts of rapidly expanding urban environments and influences of large-scale greenhouse gas emissions. 

This session solicits submissions from both the observational and modelling communities examining urban atmospheric and landscape dynamics, processes and impacts owing to urban induced climate change, the efficacy of various strategies to reduce such impacts, and techniques highlighting how cities are already using novel science data and products that facilitate planning and policies on urban adaptation to and mitigation of the effects of climate change. Emerging topics including, but not limited to, urban climate informatics, are highly encouraged.

The CL2.5 Session Solicited/Invited Talk will be given by Prof. Tony Brazel, recipient of the International Association of Urban Climate's Luke Howard Award, the American Meteorological Society's Helmut E. Landsberg Award, Lifetime Achievement Award of the Association of American Geographers' Climate Specialty Group, and the Jeffrey Cook Prize in Desert Architecture from Ben-Gurion University of the Negev, Israel.

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Convener: Matei Georgescu | Co-conveners: Sorin Cheval, Matthias Demuzere, Natalie TheeuwesECSECS, Hendrik WoutersECSECS
CL2.6

Detecting and attributing the fingerprint of anthropogenic climate change in long-term observed climatic trends is an active area of research. Though the science is well established for temperature related variables, the study of other climate indicators including hydrometeorological variables pose greater challenges due to their greater complexity and rarity.

Complementary to this, assessing the extent to which extreme weather events, including compound events, are attributable to anthropogenic climate change is a rapidly developing science, with emerging schools of thought on the methodology and framing of such studies. Once again, the attribution of hydrometeorological events, is less straightforward than temperature-related events. The attribution of impacts, both for long-term trends and extreme events is even more challenging.

This session solicits the latest studies from the spectrum of detection and/or attribution approaches. By considering studies over a wide range of temporal and spatial scales we aim to identify common/new methods, current challenges, and avenues for expanding the detection and attribution community. We particularly welcome submissions that compare approaches, or address hydrometerological trends, extremes and/or impacts – all of which test the limits of the present science.

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Convener: Aglae JezequelECSECS | Co-conveners: Seung-Ki Min, Pardeep Pall, Aurélien Ribes
ITS2.16/NH10.6

High-impact climate and weather events typically result from the interaction of multiple hazards across various spatial and temporal scales. These events, also known as Compound Events, often cause more severe socio-economic impacts than single-hazard events, rendering traditional univariate extreme event analyses and risk assessment techniques insufficient. It is therefore crucial to develop new methodologies that account for the possible interaction of multiple physical drivers when analysing high-impact events. Such an endeavour requires (i) a deeper understanding of the interplay of mechanisms causing Compound Events and (ii) an evaluation of the performance of climate/weather, statistical and impact models in representing Compound Events.

The European COST Action DAMOCLES coordinates these efforts by building a research network consisting of climate scientists, impact modellers, statisticians, and stakeholders. This session creates a platform for this network and acts as an introduction of the work related to DAMOCLES to the research community.

We invite papers studying all aspects of Compound Events, which might relate to (but are not limited to) the following topics:

Synthesis and Analysis: What are common features for different classes of Compound Events? Which climate variables need to be assessed jointly in order to address related impacts? How much is currently known about the dependence between these variables?
Stakeholders and science-user interface: Which events are most relevant for stakeholders? What are novel approaches to ensure continuous stakeholder engagement?
Impacts: What are the currently available sources of impact data? How can they be used to link observed impacts to climate and weather events?
Statistical approaches, model development and evaluation: What are possible novel statistical models that could be applied in the assessment of Compound Events?
Realistic model simulations of events: What are the physical mechanisms behind different types of Compound Events? What type of interactions result in the joint impact of the hazards that are involved in the event? How do these interactions influence risk assessment analyses?

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Co-organized by AS1/CL2/HS12/NP2
Convener: Jakob ZscheischlerECSECS | Co-conveners: Nina Nadine RidderECSECS, Bart van den Hurk, Philip Ward, Seth Westra
CL2.8

Precipitation is an essential aspect of climate, and also drives many climate impacts. The primary tool for projecting future precipitation is climate models. Climate models are already being used, both directly and indirectly, to quantify anticipated impacts of climate for the purpose of making decisions. Improving precipitation in models requires (1) quantifying characteristics of precipitation in relevant observational datasets, (2) comprehensive comparison of climate model precipitation against observations, and (3) sustained model development efforts focus on improving precipitation in models. It also requires addressing the many characteristics of precipitation, ranging from its mean spatial pattern through its variability across timescales from hourly and diurnal extending through extreme events (whether dry or wet).

We invite presentations in this session that address:
- metrics to quantify the characteristics of precipitation in observations,
- evaluation of climate model simulations against observations, and
- development efforts aimed at improving precipitation in models (including seamless modeling systems).

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Co-organized by AS1
Convener: Angeline PendergrassECSECS | Co-conveners: Margot badorECSECS, Jennifer Catto, Gill Martin, Christian Jakob
AS1.22

The understanding of tropical phenomena and their representation in numerical models still raise important scientific and technical questions, particularly in the coupling between the dynamics and diabatic processes. Among these phenomena, tropical cyclones (TC) are of critical interest because of their societal impacts and because of uncertainties in how their characteristics (cyclogenesis processes, occurrence, intensity, latitudinal extension, translation speed) will change in the framework of global climate change. The monitoring of TCs, their forecasts at short to medium ranges, and the prediction of TC activity at extended range (15-30 days) and seasonal range are also of great societal interest.

The aim of the session is to promote discussions between scientists focusing on the physics and dynamics of tropical phenomena. This session is thus open to contributions on all aspects of tropical meteorology between the convective and planetary scale, such as:

- Tropical cyclones,
- Convective organisation,
- Diurnal variations,
- Local circulations (i.e. island, see-breeze, etc.),
- Monsoon depressions,
- Equatorial waves and other synoptic waves (African easterly waves, etc.),
- The Madden-Julian oscillation,
- etc.

We especially encourage contributions of observational analyses and modelling studies of tropical cyclones and other synoptic-scale tropical disturbances including the physics and dynamics of their formation, structure, and intensity, and mechanisms of variability of these disturbances on intraseasonal to interannual and climate time scales.

Findings from recent field campaigns such as YMC and PISTON are also encouraged.

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Co-organized by CL2/NH1
Convener: Jean Philippe Duvel | Co-conveners: Eric Maloney, Kevin ReedECSECS, Enrico Scoccimarro, Allison WingECSECS
CL2.10

The Andes is the longest cordillera in the world and extends from northern South America (11°N) to the southern tip of the continent (∼53°S). The Andes runs through seven countries and provide resources for about 90 million inhabitants. The Andes is characterized by a rich variety of mountain climates and ecosystems, producing unique contrasting climate conditions over its eastern and western sides, but also across its latitudinal extent. Currently, the Andes hydroclimate faces several threats to sustainable development, such as water supply and the sustainability of ecosystem services, including global climate change, Andes and Amazon deforestation and local land use change, glaciers retreat, human encroachment, among others). In turn, diverse hydroclimatic high-impact extreme events affect the Andean communities owing to the prevailing weather and climate patterns, steep terrain, deforestation and human occupancy. This session aims to assess and discuss recent progress in the Andes hydroclimate and identify pressing research challenges and the development of associated human capabilities. We welcome submissions based on observational and modelling approaches, from the local to the continental scales and from diurnal to interdecadal time scales. Emerging new topics are particularly welcome, including water and energy budgets, high impact events, precipitation hotspots, climate change and deforestation impacts, climate-vegetation interactions, cryosphere studies, water resources availability, connections with the Amazon and the La Plata River basins and neighboring oceans, among others.

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Co-organized by HS13
Convener: Jhan Carlo Espinoza | Co-conveners: Wouter Buytaert, Katja Trachte, Germán Poveda
AS1.24

Clouds and aerosols play a key role in climate and weather-related processes over a wide range of spatial and temporal scales. An initial forcing due to changes in the aerosol concentration and composition may also be enhanced or dampened by feedback processes such as modified cloud dynamics, surface exchange or atmospheric circulation patterns. This session aims to link research activities in observations and modelling of radiative, dynamical and microphysical processes of clouds and aerosols and their interactions. Studies addressing several aspects of the aerosol-cloud-radiation-precipitation system are encouraged.

Topic covered in this session include:
- Cloud and aerosol macro- and microphysical properties, precipitation formation mechanisms
- The role of aerosols and clouds for the radiative energy budget
- Observational constraints on aerosol-cloud interactions
- Cloud-resolving modelling
- Parameterization of cloud and aerosol microphysics/dynamics/radiation
- Use of observational simulators to constrain aerosols and clouds in models
- Experimental cloud and aerosol studies
- Aerosol, cloud and radiation interactions and feedbacks in the climate system

Invited Speakers:
Nicolas Bellouin (University of Reading)
Anna Possner (Goethe University Frankfurt)

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Co-organized by CL2
Convener: Edward GryspeerdtECSECS | Co-conveners: Annica Ekman, Wei-Kuo Tao
CL2.12

With the rapidly changing conditions in the Arctic and Antarctic, reliable weather and climate forecasts are becoming increasingly important in the polar regions due to new challenges and opportunities in the economic, touristic, transportation, and scientific sectors. Likewise, the weather and climate of the mid-latitudes are significantly affected by what happens at the poles. While the impacts of severe weather phenomena on business and infrastructure can be significant, the polar regions are yet among the least-observed areas of our planet, and model predictions are challenged by the complexity of the polar climate systems.
To enhance our models’ predictive skills, more and better use of observation systems of the polar atmosphere, sea ice, and ocean are needed. It is on these premises that the World Meteorological Organization’s project Year of Polar Prediction (YOPP) and the European Horizon2020 APPLICATE project are carrying out their activities, initiating and promoting collaboration among international institutes, operational forecasting centers and stakeholders in an effort to bring together scientific expertise and know-how to work on better polar predictive skill.
In this session, we welcome presentations on activities and results from the YOPP and APPLICATE projects as well as contributions from other projects and institutes that focus on how to best capitalise on existing and additional Arctic and Antarctic observations such as Copernicus to improve forecast initial states, verification, and model physics, and to optimise the future polar observing system.
We welcome abstracts on topics including, but not limited to: Arctic and Antarctic observations, modelling, prediction, data assimilation, verification, linkages to mid-latitudes, user engagement, and governance. New results, contributions from international projects with a focus in the polar regions, and cross-disciplinary approaches that involve natural and social sciences are particularly appreciated.

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Convener: Luisa Cristini | Co-conveners: Jonathan Day, Thomas Jung, Siri Jodha Khalsa, Jørn Kristiansen
OS1.13

In recent years the interaction between the ocean and the cryosphere in the marginal seas of the Southern Ocean has become a major focus in climate research. Questions such as "Why has Antarctic sea ice only recently begun to decline?", "What controls the inflow of warm water into ice shelf cavities and where does this destabilize the ice?", and “How do ocean and climate respond to enhanced melting of Antarctic ice?” have attracted scientific and public attention. Recent advances in observational technology, data coverage, and modeling provide scientists with a better understanding of the mechanisms involving ice-ocean interactions in the far South. Processes on the Antarctic continental shelf have been identified as missing links between the cryosphere, the global atmosphere and the deep open ocean that need to be captured in large-scale and global model simulations.

This session calls for studies of the Southern Ocean's marginal seas including the Antarctic continental shelf and ice shelf cavities. Physical and biogeochemical interactions between ice shelves, sea ice and the open ocean are of major interest, as are their impacts on the greater Antarctic climate system. This includes work on all scales, from local to basin-scale to circumpolar. Studies based on in-situ observations and remote sensing as well as regional to global models are welcome. We particularly invite cross-disciplinary topics involving physical and biological oceanography, glaciology or biogeochemistry.

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Co-organized by BG4/CL2/CR6
Convener: Xylar Asay-Davis | Co-conveners: Torge Martin, Nadine SteigerECSECS, Ralph Timmermann
ITS5.7/CL2.14

It has been shown that regional climate change interacts with many other man-made perturbations in both natural and anthropogenic coastal environments. Regional climate change is one of multiple drivers, which have a continuing impact on terrestrial, aquatic and socio-economic (resp. human) environments. These drivers interact with regional climate change in ways, which are not completely understood. Recent assessments all over the world have partly addressed this issue (e.g. Assessment of Climate Change for the Baltic Sea region, BACC (2008, 2015); North Sea Climate Change Assessment, NOSCCA (2011); Canada’s Changing Climate Report, CCCR (2019)).
This session invites contributions, which focus on the connections and interrelations between climate change and other drivers of environmental change, be it natural or human-induced, in different regional seas and coastal regions. Observation and modelling studies are welcome, which describe processes and interrelations with climate change in the atmosphere, in marine and freshwater ecosystems and biogeochemistry, coastal and terrestrial ecosystems as well as human systems. In particular, studies on socio-economic factors like aerosols, land cover, fisheries, agriculture and forestry, urban areas, coastal management, offshore energy, air quality and recreation, and their relation to climate change, are welcome.
The aim of this session is to provide an overview over the current state of knowledge of this complicated interplay of different factors, in different regional seas and coastal regions all over the world.

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Co-organized by BG4/HS12/NH10/OS2
Convener: Marcus Reckermann | Co-conveners: Ute Daewel, Helena Filipsson, Markus Meier, Markus Quante
OS1.6

Sustained observations at sea are being made within a wide variety of programmes and are leading to significant advances in our ability to understand and model climate. Further efforts to make sustained observations at the sea surface and through the water column are planned under the Global Climate Observing System (GCOS), the Global Ocean Observing System (GOOS), and the UN Decade for Ocean Research for Sustainable Development. This session will explore ongoing and planned sustained ocean observing efforts and illuminate their roles in improving understanding of climate. At the same time it seeks to probe the interfaces between observing, modelling, and the development of products. Various sustained observations are being used to obtain new insights into climate variability and to guide the development of products. For example, air-sea flux moorings are being maintained at select sites to assess models and air-sea flux fields. They also form a valuable tool to calibrate and validate remote sensing of the ocean. Deep temperature and salinity measurements are being made at time series moorings and will be made by deep ARGO floats. Moored arrays have been established to measure meridional transports. Such sustained observations provide the means to investigate model biases and errors and motivate improvements to models. This session seeks to encourage the growth of linkages between sustained ocean observing and climate modeling. In particular, we ask for contributions both on sustained observation-based studies of climate variability and present or future improved collaborations between observing and modelling.

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Co-organized by CL2
Convener: Simon Josey | Co-conveners: Rena Czeschel, Maria Valdivieso, Robert Weller
OS1.4 | PICO

The ocean's role in climate involves a rich tapestry of physical and biogeochemical processes. Water-mass transformation analyses, which exploit fundamental understanding of the ocean’s layering, are a prominent and promising means to disentangle and quantify leading processes. This session is aimed to disseminate and stimulate such analyses across oceanographic disciplines.

Water mass transformation analyses assess the state and evolution of water masses, defined as ocean layers, in combination with the driving forces of ocean circulation. By framing ocean circulation as moving layers the framework complements Eulerian and Lagrangian approaches. It has traditionally been used to analyze the steady-state overturning circulation. However, recent advances have allowed for applications of this framework to understand climate variability and the interplay of the overturning circulation and origin and fate of biogeochemical tracers. As such, the water mass transformation framework weaves together ocean dynamics, thermodynamics, biogeochemical processes, and interactions with the atmosphere, cryosphere and solid Earth.

We welcome studies that utilize water-mass analyses and the water-mass transformation framework to further our understanding of the ocean’s role in the climate system. This includes efforts to better understand processes that contribute to water mass formation, such as (sub)mesoscale air-sea fluxes or interior ocean mixing, and that have a broader perspective on water masses. We especially welcome frontier interdisciplinary applications that analyze climate variability or combine physics with biogeochemistry through water mass analyses.

Solicited speaker: Sjoerd Groeskamp

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Co-organized by BG4/CL2
Convener: Ivy FrengerECSECS | Co-conveners: Casimir de LavergneECSECS, D. Gwyn EvansECSECS
OS1.11

The rapid decline of Arctic sea ice in the last decade is a dramatic indicator of climate change. The Arctic sea ice cover is now thinner, weaker and drifts faster. The ocean is also changing; the volume of freshwater stored in the Arctic and has increased as have the inputs of coastal runoff from Siberia and Greenland. Concurrently inflows from the Atlantic and Pacific Oceans have warmed. As the global surface temperature rises, the Arctic Ocean is speculated to become seasonally ice-free in the 21st century, which prompts us to revisit our perceptions of the Arctic system as a whole. What could the Arctic look like in the future? How are the present changes in the Arctic going to affect the lower latitudes? What aspects of the changing Arctic should future observations, remote sensing and modelling programmes address? The scientific community is investing considerable effort in making the current knowledge of the physical and biogeochemical properties of the Arctic more systematic, in exploring poorly understood coupled atmosphere-sea-ice-ocean processes to improve prediction of future changes in the Arctic.

In this session, we invite contributions from a variety of studies addressing the recent past, present and future Arctic. We encourage submissions examining interactions between the ocean, atmosphere and sea ice and on studies linking changes in the Arctic to the global ocean. Submissions with a focus on emerging cryospheric, oceanic and biogeochemical processes and their implications are particularly welcome.

The session promotes results from current Arctic programmes and discussions on future plans for Arctic Ocean modelling and measurement strategies, and encourage submissions on the results from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC).

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Co-organized by AS4/BG4/CL2/CR6
Convener: Yevgeny Aksenov | Co-conveners: Paul A. Dodd, Céline Heuzé, Krissy Reeve
CL2.18

Climate variations in the tropical Atlantic Ocean are of high importance at both regional and global scales. Regionally, tropical Atlantic variability (TAV) strongly affects precipitation over Africa and South America and also modulates the Angola-Benguela and Mauritania-Senegal upwelling systems. At the global scale, TAV is able to impact the adjacent tropical oceans (e.g. increasing ENSO predictability or modulating the Indian monsoon) and remote areas, such as the Euro-Mediterranean and East-Asian sectors. However, coupled models still fail to reproduce the tropical Atlantic seasonal cycle, variability and teleconnections. Understanding the mechanisms underlying TAV as well as finding the root causes for its poor representation in global climate models is therefore an area of active research.

This session is devoted to the understanding of tropical Atlantic climate variability from interannual to multi-decadal time scales, with a special focus on its regional impacts and teleconnections to other basins. We therefore invite contributions that examine TAV with respect to its drivers, modulation on multi-decadal time scales, impacts on rainfall over the adjacent continents and coastal upwelling systems (including extremes), interactions with other ocean basins, and applications for climate services. Furthermore, we seek contributions examining the causes and impacts of systematic model errors in the region. Studies based on model simulations as well as direct observations, reanalysis or reconstructions are welcome

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Co-organized by AS1/OS1
Convener: Marta Martín-ReyECSECS | Co-conveners: Teresa Losada, Ingo Richter
CR3.2 | PICO

Snow cover characteristics (e.g. spatial distribution, surface and internal physical properties) are continuously evolving over a wide range of scales due to meteorological conditions, such as precipitation, wind and radiation.
Most processes occurring in the snow cover depend on the vertical and horizontal distribution of its physical properties, which are primarily controlled by the microstructure of snow (e.g. density, specific surface area). In turn, snow metamorphism changes the microstructure, leading to feedback loops that affect the snow cover on coarser scales. This can have far-reaching implications for a wide range of applications, including snow hydrology, weather forecasting, climate modelling, and avalanche hazard forecasting or remote sensing of snow. The characterization of snow thus demands synergetic investigations of the hierarchy of processes across the scales ranging from explicit microstructure-based studies to sub-grid parameterizations for unresolved processes in large-scale phenomena (e.g. albedo, drifting snow).

This session is therefore devoted to modelling and measuring snow processes across scales. The aim is to gather researchers from various disciplines to share their expertise on snow processes in seasonal and perennial snowpacks. We invite contributions ranging from “small” scales, as encountered in microstructure studies, over “intermediate” scales typically relevant for 1D snowpack models, up to “coarse” scales, that typically emerge for spatially distributed modelling over mountainous or polar snow- and ice-covered terrain. Specifically, we welcome contributions reporting results from field, laboratory and numerical studies of the physical and chemical evolution of snowpacks, statistical or dynamic downscaling methods of atmospheric driving data, assimilation of in-situ and remotely sensed observations, representation of sub-grid processes in coarse-scale models, and evaluation of model performance and associated uncertainties.

This session is closely linked to the session 'Snow and ice accumulation, melt, and runoff generation in catchment hydrology', which addresses monitoring and modelling of snow for hydrologic applications.

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Co-organized by AS4/CL2/HS2.1
Convener: Nora Helbig | Co-conveners: Neige CalonneECSECS, Richard L.H. Essery, Henning Loewe, Vincent Vionnet
CR5.6

Understanding the impacts of climate change on ice sheets and glaciers requires accurate knowledge of surface mass balance. The interaction of ice sheets and glaciers with the atmosphere enables coupled atmosphere-ocean modes and large-scale weather patterns, meso-scale circulations, and local-scale energy and mass exchanges in the near-surface boundary layer to control the surface mass balance. Surface processes including melt-albedo feedbacks and firn densification introduce further complexity in determining surface mass balance.

This session focuses on (i) advances in measuring surface energy budgets and surface mass balance, and (ii) modelling that improves our understanding of glacier and ice sheet surface mass balance and atmospheric interaction. We invite contributions across a broad range of theoretical, numerical and observational approaches that explore historic, recent and projected changes to glacier and ice sheet surface energy budgets and mass balance. The range of topics includes but is not limited to: boundary layer dynamics; improvements to satellite SMB retrievals; firn densification; future atmospheric circulation impacts; changes in cloudiness; and the processes driving snow and ice albedo changes. We particularly welcome contributions which focus on improvements to process understanding that will lead to better SMB estimates in the future.

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Co-organized by AS4/CL2
Convener: Andrew TedstoneECSECS | Co-conveners: Charles AmoryECSECS, Ruth Mottram, Willem Jan van de Berg
AS2.10

Atmosphere and Cryosphere are closely linked and need to be investigated as an interdisciplinary subject. Most of the cryospheric areas have undergone severe changes in last decades while such areas have been more fragile and less adaptable to global climate changes. This AS-CR session invites model- and observational-based investigations on any aspects of linkages between atmospheric processes and snow and ice on local, regional and global scales. Emphasis is given on the Arctic, high latitudes and altitudes, mountains, sea ice, Antarctic regions. In particular, we encourage studies that address aerosols (such as Black Carbon, Organic Carbon, dust, volcanic ash, diatoms, bioaerosols, bacteria, etc.) and changes in the cryosphere, e.g., effects on snow/ice melt and albedo. The session also focus on dust transport, aeolian deposition, and volcanic dust, including health, environmental or climate impacts at high latitudes, high altitudes and cold Polar Regions. We include contributions on biological and ecological sciences including dust-organisms interactions, cryoconites, bio-albedo, eco-physiological, biogeochemical and genomic studies. Related topics are light absorbing impurities, cold deserts, dust storms, long-range transport, glaciers darkening, polar ecology, and more. The scientific understanding of the AS-CR interaction needs to be addressed better and linked to the global climate predictions scenarios.

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Co-organized by CL2/CR3
Convener: Pavla Dagsson WaldhauserovaECSECS | Co-conveners: Biagio Di MauroECSECS, Outi Meinander, Marie Dumont
CR6.4

Ice-ocean-atmosphere interactions in the Weddell Sea play an important role in the formation of dense water masses and in modulating the rate of ice discharge from Antarctica. Recent ocean- and atmosphere-induced changes to the ice shelves that fringe the margins of the Weddell Sea, including the disintegration of Larsen A and B, have been linked to the acceleration, retreat and thinning of the glaciers that once drained into and sustained the ice shelves. Together with the calving of iceberg A-68 from Larsen C Ice Shelf, these phenomena have raised questions about the past and future stability of this sector, and have motivated much scientific research focused on elucidating the role of ice, ocean and atmosphere interactions in controlling rates of glaciological and oceanographic change over palaeo- to contemporary timescales. In addition, this research plays a key role in informing on-going international discussions regarding the inclusion of the Weddell Sea Sector as a marine protected area (MPA).

In light of on-going research within these themes, we welcome contributions examining the range of controls driving cryospheric, oceanic and atmospheric change in the Weddell Sea, across a range of timescales. Remotely sensed observations, model results, and fieldwork-based studies are particularly encouraged.

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Co-organized by CL2/OS1
Convener: Christine BatchelorECSECS | Co-conveners: Frazer ChristieECSECS, Katherine HutchinsonECSECS
BG3.8

A wide range of processes, covering various spatial and temporal scales, influence the response of terrestrial carbon fluxes (NEE, GPP, TER, fires, methane, lateral export) to changes in land and atmospheric moisture availability. The vegetation and soils also contribute to regulating land-atmosphere moisture fluxes (evapotranspiration, precipitation), which in turn feeds back to the water cycle and the climate system.

In an effort to synthesize our current understanding and identify knowledge gaps, this session encourages contributions exploring carbon-water interactions from multiple perspectives (remote-sensing, experimental, modelling) and covering all types of biomes (boreal, temperate and tropical forests, grasslands, wetlands, …). Contributions might include for example 1) investigating the effect of nonlinearities in the response of ecosystems to changes in weather and climate, 2) disentangling the impact of co-varying drought-driven changes to soil moisture, vapour pressure deficit, and/or temperature on land carbon fluxes, 3) using in-situ and/or satellite observations to evaluate and/or improve the representation of water-carbon interactions and biological processes in models, 4) developing and implementing new representations of plant and ecosystem response to land and atmospheric moisture stress (e.g. through plant hydraulics, optimality approaches, etc.).

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Co-organized by CL2/HS13
Convener: Vincent HumphreyECSECS | Co-conveners: Ana BastosECSECS, K.A. Novick, Markus Reichstein
BG3.17

Fire is an essential feature of terrestrial ecosystems and an important component of the Earth system. Climate, vegetation characteristics, and human activity regulate fire occurrence and spread, but fires also feedback to them in multiple ways. The mechanisms of interactions between fire, land, atmosphere, and society are complicated and remain poorly understood quantitatively. This session welcomes contributions on all aspects of links between fire, biosphere, climate, and humans to share recent advances and foster interdisciplinary discussions. We encourage all abstracts that explore the role of fire in the Earth system at any temporal and spatial scale using modeling, field and laboratory observations, and/or remote sensing, with an emphasis on studies that advance our understanding on (1) impacts of fire on weather, climate, and atmospheric chemistry, (2) interactions between fire, biogeochemical cycles, land water and energy budgets, and vegetation composition and structure, (3) influence of humans on fire and vice versa (e.g., impact of fire on air and water quality, human health, and economy), (4) fire characteristics (e.g. fire duration, emission factor, emission height, smoke transport), (5) spatial and temporal changes of fires in the past, present, and future, (6) fire products and models, and their validation and error/bias assessment, and (7) analytical tools designed to enhance situational awareness among fire practitioners and early warning systems, addressing specific needs of operational fire behavior modeling.

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Co-organized by AS4/CL2/NH7
Convener: Fang Li | Co-conveners: Niels AndelaECSECS, Angelica Feurdean, Renata Libonati, Sander Veraverbeke
BG2.24

Diverse ecosystem components are strongly linked both functionally and structurally in the landscape. However, different aquatic ecosystems and land ecosystems are often studied separately, although e.g. the fluxes of carbon, nitrogen and energy link these domains intimately together. This implies that the environmental drivers affecting one domain are easily reflected also in another. Considering the current extensive land use changes and climate change, integrated studies where aquatic and terrestrial ecosystems are studied in combination are urgently required.
This session focuses on research covering both aquatic and terrestrial domains, and especially addresses the changes imposed either by natural drivers or experimental manipulations. Specific emphasis is on research done at sites or platforms that are providing long-term, multidisciplinary data and combining that with experimentation.

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Co-organized by CL2/HS13, co-sponsored by AQUACOSM and eLTER
Convener: Jens C Nejstgaard | Co-conveners: Jaana Bäck, Katharina Makower, Terhi RasiloECSECS
G3.2

This session invites innovative Earth system and climate studies based on geodetic measuring techniques. Modern geodetic observing systems document a wide range of changes in the Earth’s solid and fluid layers at very diverging spatial and temporal scales related to processes as, e.g., glacial isostatic adjustment, the terrestrial water cycle, ocean dynamics and ice-mass balance. Different time spans of observations need to be cross-compared and combined to resolve a wide spectrum of climate-related signals. Geodetic observables are also often compared with geophysical models, which helps to explain observations, evaluate simulations, and finally merge measurements and numerical models via data assimilation.
We appreciate contributions utilizing geodetic data from diverse geodetic satellites including altimetry, gravimetry (CHAMP, GRACE, GOCE and GRACE-FO), navigation satellite systems (GNSS and DORIS) or remote sensing techniques that are based on both passive (i.e., optical and hyperspectral) and active (i.e., SAR) instruments. We welcome studies that cover a wide variety of applications of geodetic measurements and their combination to observe and model Earth system signals in hydrological, ocean, atmospheric, climate and cryospheric sciences. Any new approaches helping to separate and interpret the variety of geophysical signals are equally appreciated. Contributions working towards the newly established Inter-Commission Committee on "Geodesy for Climate Research" (ICCC) of the International Association of Geodesy (IAG) would be particularly interesting for this session.
With author consent, highlights from this session will be tweeted with a dedicated hashtag during the conference in order to increase the impact of the session.

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Co-organized by AS5/CL2/ESSI1/OS4
Convener: Anna KlosECSECS | Co-conveners: Carmen Boening, Henryk Dobslaw, Roelof RietbroekECSECS, Bert Wouters
GI1.3

Ground-acquired historical images from the late 1800s and aerial images from the early 1900s have been used for military, civil, and research purposes in natural sciences. These multi-temporal historical images have the unequalled potential for documenting the past environmental changes caused by anthropogenic and natural factors in the pre-satellite era.
The increasing availability of historical images as digitised images, together with advancements of digital photogrammetry, have heightened the interest in these data in the scientific community for assessing and reconstructing long-term surface evolution from local to landscape scale. Especially, newly evolved dense-matching algorithms from computer sciences and photogrammetry allow for unprecedented high-resolution data retrieval by reprocessing the historical imagery with these new methods.
However, despite the available volume of historical images, their full potential is not widely exploited yet. Currently, there is a lack of knowledge on the types of information that can be derived and their applications in geoscience. Furthermore, there are no clear photogrammetric workflows to automatically generate 3D (three-dimensional) information in the forms of point clouds or digital elevation models from stereo images as well as 2D products such as orthophotos. Amongst others, difficulties to deal with old camera models or missing information about the geometry of historical cameras have to be dealt with. Similarly, the quality and accuracy of this information are not fully understood.
Our goal is to create a diversified and interdisciplinary session that explores the potential of historical images, ranging from the photogrammetric techniques to the reconstruction and interpretation of 2D and 3D changes over the past. Hence, this session welcomes submissions on the use of historic imagery in a wide range of geoscience disciplines such as geomorphology, cryosphere, volcanology, bio-geosciences, and geology.

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Co-organized by EOS9/CL2/CR2/GM2/HS13/NH6
Convener: Livia PiermatteiECSECS | Co-conveners: Anette EltnerECSECS, Penelope HowECSECS, Wilfried KarelECSECS
SSP4.3

Forced by climate change across critical thresholds, regional and global ecosystems may shift abruptly and irreversibly from one state to another. The fossil record shows that Earth’s biosphere has undergone state shifts in the past, over various timescales, and therefore can do so in the future. The session hosts contributions of conservation paleobiology and stratigraphic paleobiology that make use of geohistorical records to understand and compare past and present ecosystem response to climate change.

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Co-organized by CL2
Convener: Stefano Dominici | Co-conveners: Laura CottonECSECS, Silvia Danise, Daniele Scarponi, Martin Zuschin
HS2.4.6

In the current context of global change, assessing the impact of climate variability and changes on hydrological systems and water resources is increasingly crucial for society to better-adapt to future shifts in water resources as well as extreme conditions (floods and droughts). However, hitherto, important sources of uncertainties have been neglected in forecasting climate impacts on hydrological systems, especially uncertainties associated with internal/natural climate variability, whose contribution to near-future changes could be as important as forced anthropogenic climate changes at the regional scales. Internal climate modes of variability (e.g. ENSO, NAO, AMO) and their impact on the continent are not properly reproduced in the current global climate models, leading to large underestimations of decadal climate and hydroclimatic variability at the global scale. At the same time, hydrological response strongly depends on catchment properties, whose interactions with climate variability are little understood at the decadal timescales. These factors altogether reduce significantly our ability to understand long-term hydrological variability and to improve projection and reconstruction of future and past hydrological changes on which improvement of adaption scenarios depends.
We welcome abstracts capturing recent insights for understanding past or future impacts of large-scale climate variability on hydrological systems and water resources as well as newly developed projection and reconstruction scenarios. Results from model intercomparison studies are encouraged.

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Co-organized by CL2/NH1
Convener: Bastien DieppoisECSECS | Co-conveners: Nicolas Massei, Katie SmithECSECS, Jean-Philippe Vidal
HS7.2

The assessment of precipitation variability and uncertainty is crucial in a variety of applications, such as flood risk forecasting, water resource assessments, evaluation of the hydrological impacts of climate change, determination of design floods, and hydrological modelling in general. Within this framework, this session aims to gather contributions on research, advanced applications, and future needs in the understanding and modelling of precipitation variability, and its sources of uncertainty.
Specifically, contributions focusing on one or more of the following issues are particularly welcome:
- Novel studies aimed at the assessment and representation of different sources of uncertainty versus natural variability of precipitation.
- Methods to account for different accuracy in precipitation time series, e.g. due to change and improvement of observation networks.
- Uncertainty and variability in spatially and temporally heterogeneous multi-source precipitation products.
- Estimation of precipitation variability and uncertainty at ungauged sites.
- Precipitation data assimilation.
- Process conceptualization and modelling approaches at different spatial and temporal scales, including model parameter identification and calibration, and sensitivity analyses to parameterization and scales of process representation.
- Modelling approaches based on ensemble simulations and methods for synthetic representation of precipitation variability and uncertainty.
- Scaling and scale invariance properties of precipitation fields in space and/or in time.
- Physically and statistically based approaches to downscale information from meteorological and climate models to spatial and temporal scales useful for hydrological modelling and applications.

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Co-organized by AS1/CL2/NH1/NP3
Convener: Simone Fatichi | Co-conveners: Alin Andrei Carsteanu, Roberto Deidda, Andreas Langousis, Chris Onof
AS2.8

Clouds play an important role in the polar climate due to their interaction with atmospheric radiation and their role in the hydrological cycle linking poleward water vapour transport with precipitation, thereby affecting the mass balance of the polar ice sheets. Cloud-radiative feedbacks have also an important influence on sea ice. Cloud and precipitation properties depend strongly on the atmospheric dynamics and moisture sources and transport, as well as on aerosol particles, which can act as cloud condensation and ice nuclei.

This session aims at bringing together researchers using observational and/or modeling approaches (at various scales) to improve our understanding of polar tropospheric clouds, precipitation, and related mechanisms and impacts. Contributions are invited on various relevant processes including (but not limited to):


- Drivers of cloud/precipitation microphysics at high latitudes,
- Sources of cloud nuclei both at local and long range,

- Linkages of polar clouds/precipitation to the moisture sources and transport,

- Relationship of the poleward moisture transport to processes in the tropics and extra-tropics, including extreme transport events (e.g., atmospheric rivers, moisture intrusions),

- Relationship of moisture/cloud/precipitation processes to the atmospheric dynamics, ranging from synoptic and meso-scale processes to teleconnections and climate indices,

- Role of the surface-atmosphere interaction in terms of mass, energy, and cloud nuclei particles (evaporation, precipitation, albedo changes, cloud nuclei sources, etc)
- Impacts that the clouds/precipitation in the Polar Regions have on the polar and global climate system, surface mass and energy balance, sea ice and ecosystems.

Papers including new methodologies specific to polar regions are encouraged, such as (i) improving polar cloud/precipitation parameterizations in atmospheric models, moisture transport events detection and attribution methods specifically in the high latitudes, and (ii) advancing observations of polar clouds and precipitation. We would like to emphasize collaborative observational and modeling activities, such as the Year of Polar Prediction (YOPP), Polar-CORDEX, the (AC)3 project on Arctic Amplification, SOCRATES, ACE and other campaigns in the Arctic and Southern Ocean/Antarctica, and encourage related contributions.

The session is endorsed by the SCAR Antarctic Clouds and Aerosols Action Group.


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Co-organized by CL2/CR7
Convener: Irina V. Gorodetskaya | Co-conveners: Susanne Crewell, Tom Lachlan-Cope, Nicole van Lipzig, Manfred Wendisch
HS7.9 | PICO

Traditionally, hydrologists have always considered precipitation and temperature as input to their models and evaporation as a loss. However, more than half of the evaporation globally comes back as precipitation on land. Anthropogenic pressure through land-use changes (and greenhouse gasses) alter, not only, the local hydrology, but through atmospheric water and energy feedbacks also effect the water cycle in remote locations.

This session aims to:

i. investigate the remote and local atmospheric feedbacks from human interventions such as greenhouse gasses, irrigation, deforestation, and reservoirs on the water cycle, precipitation and climate, based on observations and coupled modelling approaches.

ii. explore the implications of atmospheric feedbacks on the hydrologic cycle for land and water management. Can we favorably alter atmospheric hydrology and precipitation by means of ground based interventions of changing land cover, and thus changing evaporation, albedo and surface roughness?

Typically, studies in this session are applied studies using fundamental characteristics of the atmospheric branch of the hydrologic cycle on different scales. These fundamentals include, but are not limited to, atmospheric circulation, humidity, residence times, recycling ratios, sources and sinks of atmospheric moisture, energy balance and climatic extremes. Studies may also evaluate different sources of data for atmospheric hydrology and implications for inter-comparison and meta-analysis. For example, observations networks, isotopic studies, conceptual models, back-trajectories, reanalysis and fully coupled earth system model simulations.

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Co-organized by AS4/CL2
Convener: Ruud van der EntECSECS | Co-conveners: Gonzalo Miguez Macho, Lan Wang-ErlandssonECSECS
HS7.3 | PICO

Hydroclimatic conditions and the availability of water resources in space and time constitute important factors for maintaining an adequate food supply, the quality of the environment, and the welfare of inhabitants, in the context of sustainable growth and economic development. This session is designed to explore the impacts of hydroclimatic variability, climate change, and the temporal and spatial availability of water resources on: food production, population health, the quality of the environment, and the welfare of local ecosystems. We particularly welcome submissions on the following topics:

Complex inter-linkages between hydroclimatic conditions, food production, and population health, including: extreme weather events, surface and subsurface water resources, surface temperatures, and their impacts on food security, livelihoods, and water- and food-borne illnesses in urban and rural environments.

Quantitative assessment of surface-water and groundwater resources, and their contribution to agricultural system and ecosystem statuses.

Spatiotemporal modeling of the availability of water resources, flooding, droughts, and climate change, in the context of water quality and usage for food production, agricultural irrigation, and health impacts over a wide range of spatiotemporal scales

Intelligent infrastructure for water usage, irrigation, environmental and ecological health monitoring, such as development of advanced sensors, remote sensing, data collection, and associated modeling approaches.

Modelling tools for organizing integrated solutions for water, precision agriculture, ecosystem health monitoring, and characterization of environmental conditions.

Water re-allocation and treatment for agricultural, environmental, and health related purposes.

Impact assessment of water-related natural disasters, and anthropogenic forcings (e.g. inappropriate agricultural practices, and land usage) on the natural environment; e.g. health impacts from water and air, fragmentation of habitats, etc.

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Co-organized by CL2/ERE7/NH10
Convener: George Christakos | Co-conveners: Alin Andrei Carsteanu, Andreas Langousis, Hwa-Lung Yu
HS10.12

Changes in land uses may have heavy consequences on many environmental issues, such as water shortage and quality decay, biodiversity losses and soil degradation. Also climate change, resulting from the increase in greenhouse gas emissions, determines strong modifications on the environment, with particular impacts on water resources availability. The future climate trends on a planetary scale, showing significant increase in the temperature and a reduction in precipitation, will heavily impact the hydrological and ecological processes at local and global scales.
The combination of land use and climate changes is expected to have more than an additive effect on the ecosystem. The high risks of damages on soil, water, and life of plants, animals and human lives need much attention, in order to predict the negative effects on the ecosystems and plan the mitigation countermeasures. A modelling approach and the proposal of mitigation actions may be key tools to evaluate and reduce the expected impacts of land use and climate changes.
The proposed session aims to: (i) enhance a better comprehension of the geomorphological, hydrological and ecological effects induced by land use and climate changes at both planetary and local scales; (ii) optimise the traditional analytical techniques and propose novel evaluation methods of ongoing and future trends (e.g., monitoring by remote sensing, weather forecast and hydrological models); (iii) propose and experiment innovative and efficient management practices (such as eco-friendly restoration techniques and soil conservation models with low hydrological impacts), contributing to the mitigation of soil and water degradation rates under different climate and land use scenarios.
Contributions to this session about the analysis of the state-of-the-art of and new ideas and measures for mitigation of impacts of climate and land use changes in different ecosystems are welcome. Gathering the community of scientists and technicians will allow sharing of experiences and proposals (e.g., detailed field feedback, high quality laboratory works, validated numerical modelling and effectiveness assessments) to make clearer the complex interactions between ecological elements, geomorphic processes and engineering activities and suggest new guidelines to land planners and hydro-geological risk managers.

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Co-organized by CL2/GM2/SSS10
Convener: Demetrio Antonio Zema | Co-convener: Manuel Esteban Lucas-Borja
ITS5.5/NH9.23

Climate change poses risks to (re)insurers through potentially increasing the physical damage to insured assets through extreme weather events. This has been recognised by the industry but due to the short-term nature of insurance contracts has not been widely considered directly in pricing and capital management. Recent regulatory pressure and attribution studies implicating climate in several recent natural disasters is changing the industry landscape towards greater recognition of the importance of considering climate change. Questions also remain around the role of natural variability versus climate change when considering natural catastrophes; for example in the recent quiet period of winter season North Atlantic storms in north-western Europe.

The focus of the session is on atmospheric perils such as flooding, windstorm, hail and temperature extremes. This session welcomes submissions from scientists, (re)insurers and other risk management professionals on the topic of catastrophe modelling, risk assessment, risk management and pricing in the context of climate change and natural variability. In particular, talks are welcomed on methods to incorporate climate change into the modelling by insurers and reinsurers. The session also welcomes contributions regarding the impacts and importance of natural variability relative to climate change in the context of risk management.

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Co-organized by AS5/CL2/HS12
Convener: Aleksandra BorodinaECSECS | Co-conveners: Symeon Koumoutsaris, Jessica Turner
ITS3.2/NH10.7

Extreme climate and weather events, associated disasters and emergent risks are becoming increasingly critical in the context of global environmental change. They are a potential major threat to reaching the Sustainable Development Goals (SDGs) and one of the most pressing challenges for future human well-being.
This session explores the linkages between extreme climate and weather events, associated disasters, societal dynamics and resilience.
Emphasis is laid on 1) Which impacts are caused by extreme climate events (including risks emerging from compound events) and cascades of impacts on various aspects of ecosystems and societies? 2) Which feedbacks across ecosystems, infrastructures and societies exist? 3) What are key obstacles towards societal resilience and reaching the SDGs, while facing climate extremes? 4) What can we learn from past experiences? 5) What local to global governance arrangements best support equitable and sustainable risk reduction?
We welcome empirical, theoretical and modelling studies from local to global scale from the fields of natural sciences, social sciences, humanities and related disciplines.

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Co-organized by BG1/CL2/NP8, co-sponsored by Future Earth
Convener: Markus Reichstein | Co-conveners: Dorothea Frank, Felix Riede, Jana Sillmann
NP2.3 | PICO

Papers are solicited related to the understanding and prediction of weather, climate and geophysical extremes, from both an applied sciences and theoretical viewpoint.

In this session we propose to group together the traditional geophysical sciences and more mathematical/statistical approaches to the study of extremes. We aim to highlight the complementary nature of these two viewpoints, with the aim of gaining a deeper understanding of extreme events.

Potential topics of interest include but are not limited to the following:

· How extremes have varied or are likely to vary under climate change;
· How well climate models capture extreme events;
· Attribution of extreme events;
· Emergent constraints on extremes;
· Linking dynamical systems extremes to geophysical extremes;
· Extremes in dynamical systems;
· Downscaling of weather and climate extremes.
· Linking the dynamics of climate extremes to their impacts

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Co-organized by AS4/CL2/NH10
Convener: Davide FarandaECSECS | Co-conveners: Carmen Alvarez-CastroECSECS, Gabriele MessoriECSECS
NP2.2

Extreme climatic events such as heat waves, droughts, storms, extreme precipitation, floods and hurricanes impose high risks for ecosystems, agriculture, and human society in general. Such events often do not occur in isolation, but exhibit characteristic spatiotemporal patterns on regional to global scales. Moreover, impacts are largely amplified when a multitude of different events occur simultaneously or in sequence. Understanding the mechanisms leading to persistence, (long-ranged) spatial correlations and coupling of extremes, as well as how these might change in a warming climate, is therefore of high relevance.

Disentangling cause and effect, separating anthropogenic effects from low-frequency natural variability in the statistics, and probing the representation of extreme events and their teleconnections in state-of-art weather and climate models remains challenging, in particular when taking a systemic viewpoint to the analysis of the events. The application of techniques and ideas from newly arising mathematical fields such as the study of multivariate and compound extremes, new conceptual and modelling frameworks for attribution, and the exploitation of advanced statistical tools such as complex networks to extract information from large datasets might constitute a way forward.

This interdisciplinary session invites contributions relevant for weather and climate extremes, ranging from the underlying statistical theory to observation and model based studies, for present day climate and future projections.

We are particularly interested in submissions focussing on:

- Global-scale atmospheric patterns favouring the occurrence of concurrent extremes and teleconnections
- Statistical methods that allow for the identification of multivariate or compound extremes
- Attribution and storyline studies, and approaches to identify causal relations for extreme events
- The representation of extremes and their teleconnections in the CMIP6 models and related uncertainties
- Validation strategies for assessing the representation of extreme events in numerical models to decrease the uncertainty of future projections
- Data-driven and machine learning approaches to study extremes and associated teleconnections


Invited Speaker: Ted Shepherd (confirmed)

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Co-organized by CL2
Convener: Kai KornhuberECSECS | Co-conveners: Niklas BoersECSECS, Catrin Ciemer, Francesco Ragone
ITS4.5/GI1.4

Environmental systems often span spatial and temporal scales covering different orders of magnitude. The session is oriented in collecting studies relevant to understand multiscale aspects of these systems and in proposing adequate multi-platform and inter-disciplinary surveillance networks monitoring tools systems. It is especially aimed to emphasize the interaction between environmental processes occurring at different scales. In particular, a special attention is devoted to the studies focused on the development of new techniques and integrated instrumentation for multiscale monitoring high natural risk areas, such as: volcanic, seismic, energy exploitation, slope instability, floods, coastal instability, climate changes and other environmental context.
We expect contributions derived from several disciplines, such as applied geophysics, geology, seismology, geodesy, geochemistry, remote and proximal sensing, volcanology, geotechnical, soil science, marine geology, oceanography, climatology and meteorology. In this context, the contributions in analytical and numerical modeling of geological and environmental processes are also expected.
Finally, we stress that the inter-disciplinary studies that highlight the multiscale properties of natural processes analyzed and monitored by using several methodologies are welcome.

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Co-organized by AS4/CL2/GM2/GMPV9/NH8/NP3/OS4/SM5/SSS10
Convener: Pietro Tizzani | Co-conveners: Francesca Bianco, Antonello Bonfante, Raffaele Castaldo, Nemesio M. Pérez
ITS2.14/GMPV10.3

Volcanoes release gas effluents and aerosol particles into the atmosphere during eruptive episodes and by quiescent emissions. Volcanic degassing exerts a dominant role in forcing the timing and nature of volcanic unrest and eruptions. Understanding the exsolution processes of gas species dissolved in magma, and measuring their emissions is crucial to characterise eruptive mechanism and evaluate the sub-sequent impacts on the atmospheric composition, the environment and the biosphere. Emissions range from silent exhalation through soils to astonishing eruptive clouds that release gas and particles effluents into the atmosphere, potentially exerting a strong impact on the Earth’s radiation budget and climate over a range of temporal and spatial scales. Through direct exposure and indirect effects, volcanic emissions may influence local-to-regional air quality, seriously affect the biosphere and environment, and the release of gas from soil may pose long-term health hazards. Gas emissions are measured and monitored via a range of in-situ and remote sensing techniques, to gain insights into both the subterranean-surface processes and quantify the extent of their impacts. In addition, modelling of the subsurface and atmospheric processes, as well as laboratory experiments, are fundamental to the interpretation of the field-based and satellite observations. This session focuses on the state of the art and interdisciplinary science concerning all aspects of volcanic degassing and impacts of relevance to the Volcanology, Environmental, Atmospheric and Climate sciences (including regional climate), and Hazard assessment. We invite contribution on all aspects of volcanic plumes science, their observation, modelling and impacts.

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Co-organized by AS5/BG2/CL2/NH2
Convener: Pasquale Sellitto | Co-conveners: Evgenia IlyinskayaECSECS, Emily Mason, Tjarda Roberts, Giuseppe G. Salerno
ITS2.15/BG2.25

This session is linked to the Pan-Eurasian EXperiment (PEEX; www.atm.helsinki.fi/peex), a multi-disciplinary, -scale and -component climate change, air quality, environment and research infrastructure and capacity building programme. It is aimed at resolving major uncertainties in Earth system science and global sustainability issues concerning the Arctic, Northern Eurasia and China regions. This session aims to bring together researchers interested in (i) understanding environmental changes effecting in pristine and industrialized Pan-Eurasian environments (system understanding); (ii) determining relevant environmental, climatic, and other processes in Arctic-boreal regions (process understanding); (iii) the further development of the long-term, continuous and comprehensive ground-based, air/seaborne research infrastructures together with satellite data (observation component); (iv) to develop new datasets and archives of the continuous, comprehensive data flows in a joint manner (data component); (v) to implement validated and harmonized data products in models of appropriate spatio-temporal scales and topical focus (modeling component); (vi) to evaluate impact on society though assessment, scenarios, services, innovations and new technologies (society component).
List of topics:
• Ground-based and satellite observations and datasets for atmospheric composition in Northern Eurasia and China
• Impacts on environment, ecosystems, human health due to atmospheric transport, dispersion, deposition and chemical transformations of air pollutants in Arctic-boreal regions
• New approaches and methods on measurements and modelling in Arctic conditions;
• Improvements in natural and anthropogenic emission inventories for Arctic-boreal regions
• Physical, chemical and biological processes in a northern context
• Aerosol formation-growth, aerosol-cloud-climate interactions, radiative forcing, feedbacks in Arctic, Siberia, China;
• Short lived pollutants and climate forcers, permafrost, forest fires effects
• Carbon dioxide and methane, ecosystem carbon cycle
• Socio-economical changes in Northern Eurasia and China regions.
PEEX session is co-organized with the Digital Belt and Road Program (DBAR), abstracts welcome on topics:
• Big Earth Data approaches on facilitating synergy between DBAR activities & PEEX multi-disciplinary regime
• Understanding and remote connection of last decades changes of environment over High Asia and Arctic regions, both land and ocean.

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Co-organized by AS4/CL2/CR7/GI6
Convener: Markku Kulmala | Co-conveners: Alexander Baklanov, Hanna Lappalainen, Sergej Zilitinkevich
OS1.8

The Atlantic Ocean is known to exert a huge control and hence a decisive role on the surface climate over the neighbouring continents as well as that of the Arctic Ocean. Water masses from both the Pacific and Indian Oceans enter in the South Atlantic and are carried northward to higher latitudes along the main current systems to the deep water formation regions, i.e. where the atmosphere is in direct contact with the deep ocean. Understanding what drives variability on multiple time scales and long-term trends in the circulation of the Atlantic Ocean is thus imperative for more confident predictions of the climate in the future.

This session will thus focus on the dynamics, variability and trends along the key climatic current systems from the South Atlantic to the North Atlantic and Arctic Ocean and how they are driven by local-, large- or global-scale processes or teleconnections. We aim to bring together researchers using observations, ocean models and state-of-the-art climate models.

We welcome presentations focusing on

- Pathways and connectivity of water masses in the Atlantic Ocean and their variability
- Sources of heat and freshwater anomalies and their role for the Atlantic Meridional Overturning Circulation (AMOC)
- Impact of large- and global-scale atmospheric modes on the Atlantic ocean circulation
- Atlantic ocean circulation and influence on on sea-level and sea-ice change

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Co-organized by CL2
Convener: Léon ChafikECSECS | Co-conveners: Joakim KjellssonECSECS, Iselin Medhaug, Gilles Reverdin
AS1.2

This session invites contribution for presentations of high resolution weather and climate model simulations. This includes the latest state-of-the-art storm-resolving simulations (e.g. from the DYAMAND project), high-resolution climate models (e.g. from the PRIMAVERA project) but also large-eddy simulations and high-resolution ocean modelling. Presentations cover developments to improve model fidelity (e.g. via improved parametrisations), detailed studies of modeled phenomena (e.g. tropical cyclones) but also computational and model development challenges (e.g. the use of GPUs or the development of new dynamical cores).

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Co-organized by CL2/OS4
Convener: Peter Düben | Co-convener: Daniel Klocke
CL2.44

This session explores advances and challenges in convection-permitting atmospheric modelling: the newest generation of atmospheric models that allow for the explicit treatment of convective processes (grid spacing ≤ 4 km).

Convection-permitting models (CPMs) are a rapidly growing research area and improve both the diurnal convective cycle and the representation of convective precipitation, particularly extremes. CPMs often exhibit important differences in feedback mechanisms and climate change signals compared to coarser models. CPMs thus offer a promising tool to better understand fine-scale processes and provide critical information to end users, especially in areas affected by convective extremes, and have thus sparked wider interest in their applications and development. For example, the CORDEX-FPS on convective phenomena over Europe and the Mediterranean.

The session brings together numerical modellers, the observational community, cloud physicists, forecasters and CORDEX-FPS participants, with the aim of advancing understanding of convection and high-resolution modelling in general (including convective storm life cycle and convective organization) with new modelling and statistical observation approaches. Contributions on new high-resolution/sub-daily observational datasets, and their application to CPM evaluation, are particularly welcome. This session calls for papers on state-of-the-art development and application of CPM activities, including examination of interactions between convection and other atmospheric phenomena (e.g. boundary layers, cloud physics, radiation), as well as CPM investigations of local- to regional-scale phenomena (e.g. land-use change, land-ocean contrasts, flow-orography interactions, urban-rural transitions, aerosol effects, etc.). We welcome studies of past, present or future climates, and CPM modelling across time scales. Particular attention is given to extremes.

Other topics include, but are not limited to:
-- Model setup and parametrization, including sensitivity to resolution and dynamics
-- Model evaluation and new evaluation metrics/methods
-- Ensemble-based approaches to quantify uncertainty at convective scale
-- Physical understanding of added value over coarser models
-- Land-atmosphere coupling at convection-permitting scale
-- Climate studies
-- Tropical phenomena
-- Convection, energy balance and hydrological cycle
-- Lightning in CPMs
-- Teleconnection across scales
-- Novel high-resolution experiments

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Co-organized by AS1
Convener: Stefan Sobolowski | Co-conveners: Hayley Fowler, Douglas Maraun, Timothy RaupachECSECS, Merja Tölle
AS4.6

The atmospheric water cycle is a key component of the climate system, and links across many scientific disciplines. Processes interact with dynamics at different scales throughout the atmospheric life cycle of water vapour from evaporation to precipitation. This session sets the focus on understanding the interaction between processes, their dynamics and characteristics of the water cycle, covering the entire atmospheric life cycle from evaporation, atmospheric moisture transport, to precipitation processes as observed from in-situ and remote sensing instrumentation, recorded by (paleo)climate archives, and as simulated by models for past, present and future climates.

We invite studies

* focusing on the understanding and impacts of features of the atmospheric water cycle related to weather systems, such as Atmospheric Rivers, Cold-Air Outbreaks, Warm Conveyor Belts, Tropical Moisture Exports, and the global Monsoon systems;

* investigating the large-scale drivers behind the variability and trends within the atmospheric water cycle, from long-term observations, reanalysis data, or regional to global model simulations;

* involving and connecting field campaigns (YOPP, MOZAiC, NAWDEX) with forecast and reanalysis data, indicators of past hydroclimate from climate proxies such as ice cores and stalagmites, and model predictions of the future evolution of the atmospheric water cycle;

* applying methods such as stable isotopes as physical tracers in the water cycle, tagged water tracers, and Lagrangian moisture source diagnostics to identify source-sink relationships and to evaluate model simulations of the water cycle;

* describing the global and regional state of the atmospheric water cycle with characteristics such as the recycling ratio, life time of water vapour, and moisture transport properties.

We particularly encourage contributions to link across neighbouring disciplines, such as atmospheric science, climate, paleoclimate, glaciology, and hydrology.

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Co-organized by CL2/HS13
Convener: Harald Sodemann | Co-conveners: Marie-Estelle DemoryECSECS, Irina V. Gorodetskaya, David Lavers, Alexandre M. RamosECSECS
AS1.15 | PICO

Recent extreme weather and climate episodes, including the European heatwaves of summer 2003 and June/July 2019, highlight the need to further our understanding of linear and non-linear (quasi-stationary) planetary and synoptic-scale Rossby wave dynamics in the atmosphere, and their impacts on weather and climate events. Abstracts are solicited that are dedicated to:
i) the dynamics of linear wave propagation or quasi-stationarity, of wave breaking, atmospheric blocking, or jets as atmospheric Rossby waveguides. This includes the role of local and remote drivers (e.g., the tropics, Arctic, or stratosphere).
ii) exploring the links between extreme weather/climate events and linear and non-linear Rossby waves, including wave breaking and/or blocking.
iii) quantifying model representation of Rossby waves in climate and numerical weather prediction models, including wave propagation and breaking.
iv) exploring the role of Rossby wave trains on predictability at lead times from medium range (~2 weeks) to seasonal time-scales. This includes blocking and wave propagation.
v) analyzing projected future changes in planetary or synoptic-scale Rossby waves, or in their future impacts on weather and climate events.

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Co-organized by CL2
Convener: Rachel White | Co-conveners: Kai KornhuberECSECS, Olivia Romppainen-Martius, Volkmar Wirth
AS4.2

Several large ensemble model simulations from General Circulation Models (GCM), Earth System Models (ESM), or Regional Climate Models (RCM), have been generated over the recent years to investigate internal variability and forced changes of the climate system - and to aid the interpretation of the observational record by providing a range of historical climate trajectories that could have been. The increased availability of large ensembles also enables broadening their application to new and inter-disciplinary fields.

This session invites studies using large GCM, ESM, or RCM ensembles looking at the following topics: 1) forced changes in internal variability and reinterpretation of observed record; 2) development of new approaches to attribution of observed events or trends; 3) impacts of natural climate variability; 4) assessment of extreme and compound event occurrence; 5) use of large ensembles for robust decision making; 6) large ensembles as testbeds for method development; and 7) novel methods for efficient analysis and post-processing of large ensembles.

We welcome research across the components of the Earth system and particularly invite studies that apply novel methods or cross-disciplinary approaches to leverage the potential of large ensembles.

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Co-organized by CL2/HS13
Convener: Flavio LehnerECSECS | Co-conveners: Andrea DittusECSECS, Ralf Ludwig, Laura Suarez-GutierrezECSECS, Karin van der WielECSECS
AS1.10

This session welcomes contributions on predicting climate variability on different time-scales (seasonal to decadal and beyond) using realistically initialized climate model ensemble simulations. Particularly, we invite studies assessing different aspects of climate predictability, including extremes, and pinning down the respective sources of predictability. According to the calendar season, the geographical domain and the time-scale of the forecast, different climate realms (e.g. ocean, cryosphere, or land) may be key for predictability. There is a certain focus also on predicting large-scale atmospheric circulation anomalies associated to teleconnections, in the tropics but also in the mid-latitudes, which allow, or in the future may allow, climate-related applications to be run operationally in a wide range of disciplines. This session aims to embrace advances in our understanding of the origins of seasonal to decadal predictability, as well as in improving the respective forecast skill and making the most of this information by building and testing new applications and climate services. Last but not least, we welcome studies on state-of-the-art techniques assisting ensemble prediction, such as subsampling and forecast evaluation conditioned on the initial climate state.

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Co-organized by CL2/OS4
Convener: Panos Athanasiadis | Co-convener: Leon Hermanson
NH3.12

Climate change (CC) is expected affecting weather forcing regulating the triggering, reactivation, and severity of slope failures and soil erosion. In this view, the influence of CC can be different according to the area, the time horizon of interest and to the specific trends of weather variables. Similarly, land use/cover change can play a pivotal role in exacerbating or reducing such hazards.
Thus, the overall impacts depend on the region, spatial scale, time frame and socio-economic context addressed. However, even the simple identification of the weather patterns regulating the occurrence of such phenomena represents a not trivial issue, also assuming steady conditions, due to the crucial role played by geomorphological details. To support hazards’ monitoring, predictions and projections, last-generation and updated datasets with high spatio-temporal resolution and quality - like those from the Copernicus Services’ Portals - are useful to feed models, big-data analytics and indicators’ frameworks enabling timely, robust and efficient decision making.
The Session aims at presenting studies concerning ongoing to future landslide dynamics and soil erosion hazards across different geographical contexts and scales (from slope to regional, to global scale) including analyses of historical records and related climate variables, or modeling approaches driven by future climate exploiting downscaled output of climate projections. Studies assessing variations in severity, frequency and/or timing of events and consequent risks are valuable. Finally, tested or designed adaptation strategies can be discussed.

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Co-organized by CL2/SSS2
Convener: Guido Rianna | Co-conveners: Stefano Luigi GarianoECSECS, Fausto Guzzetti, Alfredo RederECSECS, Monia Santini
GI2.4

Remote sensing, numerical models, and machine learning have been widely used for investigating environmental risks under climate change. It is known that they tend to do an excellent job in mapping, simulating, and projecting the long-term changes in average conditions. However, damages associated with extreme weathers by droughts, floods, forest fires, heat-related mortality, and crop yield loss are often more devastating than those caused by gradual climate changes. How remote sensing, numerical models, and machine learning can be used for assessing the impacts of extreme weathers on the natural and human systems remains uncertain.
This session aims to summarize current progress in assessing the ability of remote sensing, numerical models, and machine learning for quantifying climate risks in multiple sectors, such as water, agriculture, and human health.
We especially welcome investigations focusing on the inter-comparison of methodologies, as well as multi-sectoral, cross-sectoral, and integrated assessments.

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Co-organized by CL2/ESSI1/NH6
Convener: Guoyong LengECSECS | Co-conveners: Jian PengECSECS, Shengzhi Huang, Zheng DuanECSECS, Shiqiang Zhang
AS2.2

Changes in the Arctic and Antarctic climate systems are strongly related to processes in the boundary layer and their feedbacks with the free troposphere, ocean and ice. An adequate understanding and quantification of these processes is necessary to improve predictions of future changes in the polar regions and their teleconnection with mid-latitude weather and climate, including meridional transport of heat, moisture and chemical constituents. Processes include atmosphere-ocean-ice (AOI) interactions, physical and chemical snow processes (e.g. snow photochemistry), exchange of chemical constituents including biogeochemical impacts , sources of aerosol, polynya formation processes, sea ice production and loss, and cloud formation, which represent key processes for the atmosphere, ocean and the cryosphere. AOI interactions are also triggered by and have feedbacks with synoptic systems and mesoscale weather phenomena such as cold air outbreaks, katabatic winds and polar lows. Associated processes also include the effect of extreme events such as warm air advection and clouds on the surface energy budget and related boundary layer exchanges. In addition, understanding natural processes including AOI interactions is essential to understand of the background atmosphere to quantify the anthropogenic impacts. Shallow inversions, mostly during winter-time, lead to high air pollutant concentrations. Even though severe air pollution episodes are frequently observed in the Arctic, knowledge on urban emission sources, transport and atmospheric chemical processing of pollution, especially under cold and dark conditions, are poorly understood. Similarly, the polar boundary layer can involve complicated radiative processes such as shallow stable layers with fog present. In addition, polar boundary layers can mediate chemical, aerosol, and isotope exchanges between the atmosphere and the firn important to the interpretation of ice core records.
This session is intended to provide an interdisciplinary forum to bring together researchers working in the area of boundary layer processes and high-latitude weather and climate (including snow physics, air/snow chemistry, and oceanography). Cryosphere and atmospheric chemistry processes (the focus of the IGAC/SOLAS activity “CATCH” and the IGAC/IASC activity “PACES”) are highly relevant to this session. We also encourage preliminary results from field programs such as MOSAiC and other high-latitude research efforts.

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Co-organized by CL2/CR7/OS1
Convener: William Neff | Co-conveners: Jo Browse, Julia Schmale, Michael Tjernström, Gillian Young

CL3 – Future Climate

CL3.1

One of the big challenges in Earth system science consists in providing reliable climate predictions on sub-seasonal, seasonal, decadal and longer timescales. The resulting data have the potential to be translated into climate information leading to a better assessment of multi-scale global and regional climate-related risks.
The latest developments and progress in climate forecasting on subseasonal-to-decadal timescales will be discussed and evaluated in this session. This will include presentations and discussions of predictions for a time horizon of up to ten years from dynamical ensemble and statistical/empirical forecast systems, as well as the aspects required for their application: forecast quality assessment, multi-model combination, bias adjustment, downscaling, etc.
Following the new WCPR strategic plan for 2019-2029, prediction enhancements are solicited from contributions embracing climate forecasting from an Earth system science perspective. This includes the study of coupled processes, impacts of coupling and feedbacks, and analysis/verification of the coupled atmosphere-ocean, atmosphere-land, atmosphere-hydrology, atmosphere-chemistry & aerosols, atmosphere-ice, ocean-hydrology, ocean-ice, ocean-chemistry and climate-biosphere (including human component). Contributions are also sought on initialization methods that optimally use observations from different Earth system components, on assessing and mitigating the impacts of model errors on skill, and on ensemble methods.
We also encourage contributions on the use of climate predictions for climate impact assessment, demonstrations of end-user value for climate risk applications and climate-change adaptation and the development of early warning systems.

A special focus will be put on the use of operational climate predictions (C3S, NMME, S2S), results from the CMIP5-CMIP6 decadal prediction experiments, and climate-prediction research and application projects (e.g. EUCP, APPLICATE, PREFACE, MIKLIP, MEDSCOPE, SECLI-FIRM, S2S4E).

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Co-organized by NP5/OS4
Convener: Andrea Alessandri | Co-conveners: Louis-Philippe Caron, Yoshimitsu Chikamoto, Xiaosong Yang, June-Yi Lee
CL3.2

Predictions of climate from seasonal to decadal time scales will be discussed in this session. With a time horizon from a few months up to thirty years such predictions are of major importance to society, and present an interesting scientific challenge.

The session will cover dynamical as well as statistical predictions, and their combination. It will also investigate predictions from global to regional scales, and from seasonal to multidecadal time scales ("seamless prediction"). Physical processes relevant for long-term predictability will be discussed, as well as time-dependent change in prediction skill. Analysis of predictions in a multi-model environment, and ensemble forecast initialization and generation, including innovative ensemble approaches to counter initialization shocks, will be another major focus of the session. The session will pay particular attention to innovative methods of quality assessment and verification of climate predictions, post-processing of climate hind- and forecasts, and quantification and interpretation of model uncertainty. We particularly invite contributions presenting the use of seasonal-to-decadal predictions for risk assessment and adaptation.

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Convener: André Düsterhus | Co-conveners: Leonard BorchertECSECS, Deborah VerfaillieECSECS
CL3.3

Information on the future climate is an essential basis for managing the risks, as well as potential opportunities, arising from a changing climate. Typically, this information comes from state-of-the-art numerical simulations of the climate in the form of climate predictions and climate projections. For many decision-makers and policymakers the information available from climate simulations is not at the appropriate spatial and temporal scales they need to form the basis for their climate-related risk assessments or for climate action plans. Also, some decision-makers require information that spans a range of time scales from a few months or a year ahead to decades into the future. Observational and emerging constraints can help evaluate and possibly constrain model-based uncertainty ranges.

This session aims to cover the advances in providing usable and reliable climate information for Europe over the next 40 or so years. It welcomes, without being restricted to, presentations on:

• Improved methods to quantify and understand uncertainty in climate predictions and projections for Europe. This could be on spatial scales from convectively resolving to global.
• Processes which bridge time scales from beyond a season to multiple decades and methodologies to blend the output from initialised predictions and non-initialised projections
• Demonstration of added value of initialised vs non-initialised near-term climate predictions and projections using innovative verification tools
• Illustration of the value of such climate information system through applications

The session will bring together research scientists and users from a range of projects including EUCP and national initiatives with the aim of sharing experiences, novel results and initiating discussions on this emerging topic.

Solicited speakers:
David Sexton (Met Office)
James Murphy (Met Office)
Carlo Buontempo (Copernicus Climate Change Service C3S)

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Convener: Jason A. Lowe | Co-conveners: Daniel BefortECSECS, Christopher O'ReillyECSECS, Albrecht Weerts, Antje Weisheimer
ITS5.4/CL3.4

Understanding the impact of climate change on natural and socio-economic outcomes plays an important role in informing a range of national and international policies, including energy, agriculture and health. Economic models of climate impacts used to guide policy rely on multiple components: projections of future climate change, damage functions, and policy responses, each of which comes with its own modelling challenges and uncertainties.

We invite research using process-based (e.g. Integrated Assessment Models) and empirical models of climate change to investigate future impacts, together with policy evaluation to explore effective mitigation, technology and adaptation pathways. Furthermore, we invite research on changes to, and new developments of climate-economic and econometric modelling.

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Co-organized by ERE1
Convener: Luke JacksonECSECS | Co-conveners: Sam Heft-NealECSECS, Felix PretisECSECS, David Stainforth
ITS5.1/CL3.6

Remaining carbon budgets specify the quantity of CO2 that can be emitted before a given warming level (such as the 1.5 °C target) is reached, and are thus of high interest to the public and policymakers. Yet, there are many sources of uncertainty which make it challenging to deduce this finite amount of CO2 emissions. The theoretical foundation of carbon budgets is based on the concept of the Transient Climate Response to cumulative CO2 Emissions (TCRE). This is the pathway-independent ratio of global warming per unit of cumulative CO2 emissions. However, accounting for non-CO2 forcings and changes in albedo or other Earth system feedbacks provides further challenges in calculating TCRE and the remaining carbon budgets.

This session aims to further our understanding of the climate response under different emission scenarios, and to advance our knowledge of associated carbon budgets consistent with meeting various levels of warming. We invite contributions that use a variety of tools, including fully coupled Earth System Models, Integrated Assessment Models, or simple climate model emulators. We welcome studies exploring different aspects related to carbon budgets and the TCRE framework, including: the governing mechanisms behind linearity of TCRE and its limitations, effects of different forcings and feedbacks (e.g. permafrost carbon feedback) and non-CO2 forcings (e.g. aerosols, and other non-CO2 greenhouse gases), estimates of the remaining carbon budget to reach a given temperature target (for example, the 1.5 °C warming level from the Paris Agreement), the role of pathway dependence, the climate-carbon responses to different emission scenarios (e.g. SSP scenarios, or idealized scenarios), and the behaviour of TCRE in response to artificial CO2 removal from the atmosphere (i.e. negative emissions). Contributions from the fields of climate policy and economics focused on applications of carbon budgets are also encouraged.

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Co-organized by EOS4/BG1/ERE1
Convener: Katarzyna TokarskaECSECS | Co-conveners: Andrew MacDougallECSECS, Joeri Rogelj, Kirsten Zickfeld
ITS1.1/ERE7.1

The world's energy, water, and land systems are in transition and rapidly integrating, driven by forces such as socioeconomic, demographic, climatic, and technological changes as well as policies intended to meet Sustainable Development Goals (SDGs) and other societal priorities. These dynamics weave across spatial scales, connecting global markets and trends to regional and sub-regional economies. At the same time, resources are often locally managed under varying administrative jurisdictions closely tied to inherent characteristics of each commodity such as river basins for water, grid regions for electricity and land-use boundaries for agriculture. Local decisions in turn are critical in deciding the aggregate success and consequences of national and global policies. Thus, there is a growing need to better characterize the energy-water-land nexus to guide robust and consistent decision making across these scales. This session invites abstracts exploring energy-water-land dynamics, trade patterns, policy interventions, infrastructure planning and uncertainty characterization across variable spatial boundaries.

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Co-organized by CL3/HS12/SSS12
Convener: Zarrar KhanECSECS | Co-conveners: Edo Abraham, Edward A. ByersECSECS, Saket Pande
ITS5.2/AS3.17

Accurate and precise atmospheric measurements of greenhouse gas (GHG) concentrations reveal the rapid and unceasing rise of global GHG concentrations due to human activity. The resulting increases in global temperatures, sea-level, glacial retreat, and other negative impacts are clear. In response to this evidence, nations, states, and cities, private enterprises and individuals have been accelerating GHG reduction efforts while meeting the needs of global development. The urgency, complexity and economic implications of GHG reductions demand strategic investment in science-based information for planning and tracking emission reduction policies and actions. In response, the World Meteorological Organization (WMO) Global Atmosphere Watch Program (GAW) and its partners have initiated the development of an Integrated Global Greenhouse Gas Information System (IG3IS). IG3IS combines atmospheric GHG concentration measurements and human-activity data in an inverse modeling framework to help decision-makers take better-informed action to reduce emissions of greenhouse gases and pollutants that reduce air quality. This service is based on existing and successful measurement and analysis methods and use-cases for which the scientific and technical skill is proven or emerging.

This session intends to gather presentations from researchers and decision-makers (user-community) on the development, implementation and use of atmospheric measurement-based “top-down” and data-driven “bottom-up” GHG emission inventory estimates, and the combination of both approaches, explicit in space and time, to deliver actionable emissions information at scales where human activity occurs and emission reduction is most effective. This session will also showcase the new projects and efforts to develop “good-practice” standards under the World Meteorological Organization (WMO) Integrated Global Greenhouse Gas Information System (IG3IS), which is part of WMO’s commitment to science-based services.

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Co-organized by BG2/CL3/ERE1
Convener: Phil DeCola | Co-conveners: Thomas Lauvaux, Kimberly Mueller, Tomohiro Oda, Oksana Tarasova
ITS3.5/CL3.9

Earth system resilience critically depends on the nonlinear interplay of positive and negative feedbacks of biophysical processes. Earth system science has established a robust understanding of dynamics in the carbon cycle, large-scale ecosystems, atmosphere, ocean, and cryosphere. Recent developments in policy, including the UN Sustainable Development Goals and the Paris Agreement on climate, and also in cross-discipline scientific debate about entering the Anthropocene have recognised the need for better understanding and characterization of the resilience of the Earth system to planetary-scale human impacts.

Maintaining Earth in the Holocene-like conditions that have enabled the development of the world’s societies will require better understanding of tipping dynamics in both the human world and the biophysical Earth. Societies will need to embark on rapid global-scale socio-economic transformations, to reduce the risk of crossing tipping points in the Earth system, potentially triggering cascading changes at multiple temporal and spatial scales.

Earth resilience brings the complex dynamics and perturbations associated with human activities into Earth system analysis, and increasingly captures socio-economic as well as biophysical dynamics. In this session we invite contributions on all topics relating to Earth resilience, such as assessing the biophysical and social determinants of the Earth’s long-term stability, modelling and analysis of nonlinearity, feedback processes, tipping points and abrupt shifts in the Earth system, and the potential for rapid social transformations to global sustainability.

Invited Speaker: Prof. Markus Reichstein, MPI-Biogeochemistry Jena

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Co-organized by BG1/CR7/NP8/OS1
Convener: David Armstrong McKayECSECS | Co-conveners: Sarah Cornell, Jonathan Donges, James Dyke, Ricarda Winkelmann
ITS2.10/NP3.3

Last year sessions ITS6.1-3 on urban geosciences have largely confirmed the urgency to develop inter-/trans-disciplinary approaches of urban geosciences to respond to the huge societal demand to radically improve urban systems and their interactions with their environment and climate. The session ITS.6.1 focussed on the need to develop holistic approaches going beyond specialised domains such as urban meteorology, hydrology, climatology, ecology and resilience to grasp the urban-geophysical systems in their multi-component and multiscale complexity. This in particular indispensable to resolve long lasting questions like multi-hazard threats and upscaling of climate solutions. The recent IPCC report 1.5°C confirms the necessity to fully take into account the multi-component complexity of the urban-geophysical systems to achieve the urban and infrastructure transition, one of the main four system transitions to be achieved

The present session calls therefore for contributions on the development transdisciplinary concepts, methodologies and tools, as well as their applications to urban-geophysical systems in view of this transition. Jean Jouzel (former IPCC vice-president) will open this session.

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Co-organized by CL3/ERE7/HS12, co-sponsored by AGU and JpGU
Convener: Daniel Schertzer | Co-conveners: Matthias Demuzere, Klaus Fraedrich, Gabriele ManoliECSECS, Stefano Tinti
ITS2.12/HS12.24

In an urbanizing world with major land-use changes, both human (social and economic) and natural systems and their environmental challenges and constraints need to be considered in order to achieve sustainable urban development. Nature‐based solutions (NBS) in urban areas can make anthropogenic landscapes more ecosystem-compatible, enhancing ecosystem services, preserving biodiversity, mitigating land degradation, and increasing urban resilience to environmental changes. Maintaining and restoring ecosystems and green–blue areas within urban regions is important for a) increasing the well‐being of urban populations, b) providing multifunctional services, such as storm water mitigation and local climate regulation, c) improving energy efficiency of buildings, and d) mitigating carbon emissions. Implementing NBS in urban areas is of growing importance worldwide, and particularly in the EU political agenda, as a way to attain some of the Sustainable Development Goals (e.g. Sustainable cities and communities), and to reinforce the New Urban Agenda. Implementing efficient NBS in urban landscapes requires integrated and interdisciplinary approaches.

This session aims to enhance the scientific basis for sustainable urban development and resilience and advance knowledge of innovative nature-based approaches to face environmental changes (e.g. in land use and climate) and simultaneously provide better understanding of associated social-ecological interactions. This session seeks to:

• Better understanding of advantages and disadvantages of NBS in Urban environments;
• New methods and tools to investigate the role of NBS in the context of environmental change, in particular the effectiveness of NBS in enhancing urban resilience;
• New insights and perspectives of NBS, particularly their role in providing urban ecosystem services, such as storm water regulation and reducing greenhouse gas emissions;
• Identifying opportunities for and barriers to implement NBS, driven by current regulatory frameworks and management practices - and how the former can be reaped and the latter overcome;
• Presenting overviews and case studies of NBS projects that also involve the private sector and market-based mechanisms;
• Interactions between NBS and the Sustainable Development Goals (SDGs);
• Approaches for integrating actors involved in landscape design and urban planning.

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Co-organized by BG2/CL3/NH8
Convener: Zahra KalantariECSECS | Co-conveners: Carla FerreiraECSECS, Haozhi PanECSECS, Omid RahmatiECSECS, Johanna SörensenECSECS
BG3.11

Land use and land cover change (LULCC), including land management, has the capacity to alter the climate by disrupting land-atmosphere fluxes of carbon, water and energy. Thus, there is a particular interest in understanding the role of LULCC as it relates to climate mitigation and adaptation strategies. Much attention has been devoted to the biogeochemical impacts of LULCC, yet there is an increasing awareness that the biogeophysical mechanisms (e.g. changes in surface properties such as albedo, roughness and evapotranspiration) should also be considered in climate change assessments of LULCC impacts on weather and climate. However, characterizing biogeophysical land-climate interactions remains challenging due to their complexity. If a cooling or a warming signal emerges depends on which of the biogeophysical processes dominates and on the size and pattern of the LULCC perturbation. Recent advances exploiting Earth system modelling and Earth observation tools are opening new possibilities to better describe LULCC and its effects at multiple temporal and spatial scales. This session invites studies that improve our general understanding of climate perturbations connected to LULCC from both biogeophysical and biogeochemical standpoints, and particularly those focusing on their intersection. This includes studies focusing on LULCC that can inform land-based climate mitigation and adaptation policies. Both observation-based and model-based analyses at local to global scales are welcome.

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Co-organized by CL3
Convener: Gregory Duveiller | Co-conveners: Ryan Bright, Edouard Davin, Alan Di Vittorio, Julia Pongratz
HS8.2.2

Groundwater is the world's most important, best protected and most exploited freshwater resource. It is intensively used by man. It is the prime source for drinking water supply and irrigation, hence critical to the global water-food-energy security nexus. But also for sustaining low flow requirements and ecological values of groundwater dependent ecosystems, the contribution by groundwater flow is essential. Groundwater therefore needs to be managed wisely, protected and especially used sustainably. These requirements are also expressed in Integrated Water Resources Management concepts, as e.g. in the European Water Framework Directive. In itself this is a challenge, however under a changing environment, climate, land use, population growth, etc., this task becomes a challenge especially in the light of limited data availability and consequential uncertainties. From arid over humid to arctic regions, in every type of climate changing environmental conditions become apparent and have very different local to regional hydrological effects.
In this session we invite contributions, which identify new consequences of a changing environment for future management, protection, and sustainable use of groundwater by applying integrative modelling, including water quantity and quality investigations as well as field observational studies. Methodologies, strategies, case studies as well as quantitative techniques for dealing with uncertainty and limited data availability are of interest for this session. We welcome studies describing how groundwater resources benefit from Integrated Water Resources Management approaches. Furthermore, contributions describing case studies and innovative techniques for adaptive management and protection of groundwater resources such as artificial recharge and conjunctive use are welcome.

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Co-organized by CL3
Convener: Martin Sauter | Co-conveners: Jesús Carrera, Irina Engelhardt, Fabien MagriECSECS, Joseph Guttman
ITS5.8/SSS9.2

To meet the target of the Paris agreement and limit global average temperature increase to below 2°C above preindustrial levels, not only a reduction of greenhouse gas emission is required, but also GHG removal (negative emission technologies, NET). The latter needs to be implemented quickly within the next decades to remove 2.7 to 8.5 billion tons of carbon per year from 2030 onwards. However, large-scale (monoculture, industrial-only) approaches can have undesired negative side effects on biodiversity, ecosystem services and SDGs. Among the range of easy-and-quick to implement, SDG-friendly NETs is the production of biochar, a carbon-rich product of pyrolysis of biomass. PyCCS (pyrolysis for carbon capture and storage) is an alternative to the so-called bioenergy with carbon capture and storage (BECCS) mentioned in the last IPCC 1.5° special report. It co-generates bioenergy while serving as a decentral, low-tech rural to high-tech industrial NET approach that offers a broad spectrum of economic incentives.
The benefits of biochar use in agriculture and forestry can span enhanced plant productivity, the increase in soil C stock, the reduction of nutrient losses from soil and non-CO2 greenhouse gases´ emissions. Furthermore, many other uses have been proposed for biochar beyond its application to soil, such as animal feed supplement, its use in building materials or bioplastic production. This session aims at bringing together different uses, incentives and implementation pathways of biochar as a NET technology (including, but not limited to, agriculture).
Despite its potential, biochar seems to be underrepresented in the discussion on NET, and its success depends on its large- or rather multiple-location, asap implementation strategies. This session will focus on the current advancements of the available pyrogenic carbon capture and storage (PyCCS) technologies, and on its potential application in the contexts of the green economy. Discussions on novel implementation strategies, associated risks, C sink certification and payment and on their ecological and socio-economic impact are highly welcome.

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Co-organized by BG3/CL3/ERE1
Convener: Maurizio Ventura | Co-convener: Claudia Kammann
AS3.7

A better understanding of the role of natural aerosols in the atmosphere is essential for assessing anthropogenic radiative forcing and the climate response. Our session explores primary aerosols and those formed from precursor gases emitted by natural sources, e.g. from wildfires, deserts, volcanoes and both the marine and terrestrial biosphere. The session intends to bring together experts from different fields to assess the state-of-the-science knowledge on natural aerosols and to identify future directions to reduce uncertainty. We encourage submissions that use models across different spatial scales and consider past, present or future perspectives, as well as measurements from remote sensing, field campaigns and laboratory experiments. Questions of particular interest are, but are not limited to: How can we distinguish between truly natural aerosols and those whose emissions or formation are influenced by anthropogenic activities? How have the contributions of natural aerosols to atmospheric composition and deposition changed over time? What are the consequences of these changes? Where are the missing links in our understanding of the lifecycle of natural aerosols in the atmosphere in the absence of anthropogenic influence? Can we identify any pristine environments in the present day that can help us understand the pre-industrial atmosphere?

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Co-organized by CL3
Convener: Stephanie Fiedler | Co-conveners: Hugh Coe, Douglas Hamilton, Kerstin Schepanski, Catherine Scott
AS3.3

The chemical composition of the middle atmosphere is not only relevant for understanding radiative forcing or protection of the biosphere from harmful UV radiation, but it also has an influence on tropospheric circulation and dynamics that act as a feedback on climate. Increasing greenhouse gases are expected to modify the large-scale circulation of the stratosphere, termed Brewer-Dobson circulation (BDC), and the chemical compositions of radiatively active gases, notably ozone and water vapour, in the upper troposphere and lower stratosphere (UTLS) region. Such changes in the BDC and UTLS composition are expected to change levels of surface UV radiation, modify the radiative forcing of climate, and feedback on the dynamics both within the stratosphere and at the surface. This session is particularly interested in evidence of the direct influence of climate change upon stratospheric dynamics and chemistry, as well as indirect feedbacks from these changes back upon surface climate. We welcome abstracts focused on stratospheric composition changes on time-scales encompassing inter-annual to centennial timescales,on local to global spatial scales, future projections from chemistry climate models, and discussing changes induced by both natural and anthropogenic factors, observations, as well as theoretical studies.

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Co-organized by CL3
Convener: Gabriel ChiodoECSECS | Co-conveners: William Ball, Mohamadou Diallo

CL4 – Past, Present & Future Climates

ITS3.1/NP1.2

Several subsystems of the Earth system have been suggested to react abruptly at critical levels of anthropogenic forcing. Well-known examples of such Tipping Elements include the Atlantic Meridional Overturning Circulation, the polar ice sheets and sea ice, tropical and boreal forests, as well as the Asian monsoon systems. Interactions between the different Tipping Elements may either have stabilizing or destabilizing effects on the other subsystems, potentially leading to cascades of abrupt transitions. The critical forcing levels at which abrupt transitions occur have recently been associated with Tipping Points.

It is paramount to determine the critical forcing levels (and the associated uncertainties) beyond which the systems in question will abruptly change their state, with potentially devastating climatic, ecological, and societal impacts. For this purpose, we need to substantially enhance our understanding of the dynamics of the Tipping Elements and their interactions, on the basis of paleoclimatic evidence, present-day observations, and models spanning the entire hierarchy of complexity. Moreover, to be able to mitigate - or prepare for - potential future transitions, early warning signals have to be identified and monitored in both observations and models.

This interdisciplinary session invites contributions that address Tipping Points in the Earth system from the different perspectives of all relevant disciplines, including

- the mathematical theory of abrupt transitions in (random) dynamical systems,
- paleoclimatic studies of past abrupt transitions,
- data-driven and process-based modelling of past and future transitions,
- early-warning signals
- the implications of abrupt transitions for Climate sensitivity and response,
- ecological and societal impacts, as well as
- decision theory in the presence of uncertain Tipping Point estimates

Confirmed invited speaker: Michael Ghil

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Co-organized by CL4/CR7/OS1
Convener: Niklas BoersECSECS | Co-conveners: Peter Ditlevsen, Timothy Lenton , Anna von der Heydt, Ricarda Winkelmann
CL4.2

State of the art climate models are now run for past, present and future climates. This has opened up the opportunity for paleoclimate modelling and data together to inform on future climate changes. To date, most research in this area has been on constraining basic metrics such a climate sensitivity. In addition, and just as importantly for mankind, the Earth's climate is highly variable on all spatial and temporal scales. These changes in variability (spatial or temporal) can impact the recurrence frequency of extreme events which can have catastrophic effects on society. Yet, it is unclear if a warmer future is one with more or less climate variability, and at which scales. A multitude of feedbacks are involved.

We welcome contributions that improve quantification, understanding and prediction of past, present and future climate and its variability. This includes contributions looking at "steady state" climate features such as climate sensitivity as well as those investigating changes in climate variability. The session is multidisciplinary and brings together studies related to atmospheric science, oceanography, glaciology and paleoclimatology to examine the complementarity of ideas and approaches. We particularly encourage submissions that combine models run for the past, present and future with data syntheses to constrain the spread of future predictions, submissions which combine models and data in the past to make strong conclusions or testable hypotheses about the future, as well as work highlighting future experiments and data required to strengthen the link to the future.

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Co-organized by AS4/CR7/OS1
Convener: Julia Hargreaves | Co-conveners: Chris Brierley, Kira Rehfeld
CL4.3 | PICO

Modelling paleoclimate states and the transitions between them represents a challenge for models of all complexities. At the same time, the past offers a unique possibility to thoroughly test and evaluate models that are used to simulate the present and make future climate projections.
We invite papers on paleoclimate model simulations, including time-slice (as in the Paleoclimate Modelling Intercomparison Project - PMIP) and transient simulations of climate variations on timescales ranging from millennial to glacial cycles and beyond. Presentations about results from the latest phase of PMIP4-CMIP6 are particularly encouraged. However, comparisons of different models (comprehensive GCMs, EMICs and/or conceptual models), between different periods, and between models and data, including an analysis of the underlying mechanisms, are all within the scope of the session.

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Convener: Masa Kageyama | Co-conveners: André Paul, Julia Hargreaves, Michal Kucera
SSP1.2

Directly observable relative sea-level (RSL) indicators (e.g. shore platforms, coral reef terraces, beach deposits, etc.) are used to constrain paleo sea levels and ice sheet extents and to improve GIA models and future projections of sea-level and ice-sheet responses. Biological proxies associated with and the physical characteristics of RSL indicators can be used to infer paleoclimate and together help inform climatic change and sea-level fluctuations throughout the Pleistocene. The preservation and distribution of these records assists in understanding regional earth surface processes following their deposition.

Recent advances in sea-level studies have called for increased spatiotemporal density of RSL indicators, including submerged and near-field localities, analyzed using standard definitions and methods. This session welcomes contributions to the global record of well-constrained Pleistocene sea-level indicators and associated proxies from a variety of coastal environments, not limited to peak interglacial periods. Re-interpretations of previously described records due to advancement in methods are also welcome.

This session falls within the purview of PALSEA (PALeo constraints on SEA level rise), a PAGES-INQUA Working Group, and the ERC-funded projects, WARMCOASTS and RISeR.

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Co-organized by CL4/GM6
Convener: Deirdre RyanECSECS | Co-conveners: Victor CartelleECSECS, Kim Cohen, Alessio Rovere
CL4.5

To address societal concerns over rising sea level and extreme events, understanding the contributions behind these changes is key to predict potential impacts of sea level change on coastal communities and global economy, and is recognized as one of the Grand Challenges of our time by the World Climate Research Programme (WCRP). To continue this discussion, we welcome contributions from the international sea level community that improve our knowledge of the past and present changes in sea level, extreme events, and flooding, and produce improved predictions of their future changes. We welcome studies on various drivers of sea level change and linkages between variability in sea level, heat and freshwater content, ocean dynamics, land subsidence from natural versus anthropogenic influences, and mass exchange between the land and the ocean associated with ice sheet and glacier mass loss and changes in the terrestrial water storage. Studies focusing on future sea level changes are also encouraged, as well as those discussing potential short-, medium-, and long-term impacts on coastal and deltaic environments, as well as the global oceans.

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Convener: Svetlana Jevrejeva | Co-conveners: Mélanie Becker, Marta Marcos, Aimee Slangen, Nadya Vinogradova Shiffer
CR1.1

This session explores improvements in our understanding and quantification of past, present and future ice sheet and sea-level changes. We invite contributions about the following topics:

How to improve the reliability of the projections using observations (paleo and present), models and model intercomparison exercises (ISMIP6, and others); assessment of uncertainties and probability distributions of the ice sheets' contribution to sea level change; emerging processes; feedbacks coming from interactions between components (ice sheets, ocean, atmosphere, solid earth). We focus on the present and future (multi-centennial) Greenland and Antarctic ice sheets, but paleo-studies are encouraged if they shed a light on the mentioned topics.

This session is related to both ISMASS (http://www.climate-cryosphere.org/activities/groups/ismass) and ISMIP6 (http://www.climate-cryosphere.org/activities/targeted/ismip6).

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Co-organized by CL4/OS1, co-sponsored by CliC
Convener: Frank Pattyn | Co-conveners: Guðfinna Aðalgeirsdóttir, Helene Seroussi, Donald SlaterECSECS
CR5.4

Ice sheets play an active role in the climate system by amplifying, pacing, and potentially driving global climate change over a wide range of time scales. The impact of interactions between ice sheets and climate include changes in atmospheric and ocean temperatures and circulation, global biogeochemical cycles, the global hydrological cycle, vegetation, sea level, and land-surface albedo, which in turn cause additional feedbacks in the climate system. This session will present data and modelling results that examine ice sheet interactions with other components of the climate system over several time scales. Among other topics, issues to be addressed in this session include ice sheet-climate interactions from glacial-interglacial to millennial and centennial time scales, the role of ice sheets in Cenozoic global cooling and the mid-Pleistocene transition, reconstructions of past ice sheets and sea level, the current and future evolution of the ice sheets, and the role of ice sheets in abrupt climate change.

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Co-organized by CL4
Convener: Heiko Goelzer | Co-conveners: Philippe Huybrechts, Alexander Robinson, Ricarda Winkelmann
CR1.2

The largest single source of uncertainty in projections of future global sea level is associated with the mass balance of the Antarctic Ice Sheet (AIS). In the short-term, it cannot be stated with certainty whether the mass balance of the AIS is positive or negative; in the long-term, the possibility exists that melting of the coastal shelves around Antarctica will lead to an irreversible commitment to ongoing sea level rise. Observational and paleoclimate studies can help to reduce this uncertainty, constraining the parameterizations of physical processes within ice sheet models and allowing for improved projections of future global sea level rise. This session welcomes presentations covering all aspects of observation, paleoclimate reconstruction and modeling of the AIS. Presentations that focus on the mass balance of the AIS and its contribution towards changes in global sea level are particularly encouraged.

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Co-organized by CL4/G3/OS1
Convener: Steven Phipps | Co-conveners: Florence Colleoni, Chris Fogwill, Taryn Noble
CR1.3

Recent observations and modelling of this critical region suggest an ongoing interaction between climate change, ocean circulation, and basal melting that leads to rapid ice loss. Processes that connect these components are key to understanding the future of the glacier and the likelihood of rapid, and potentially irreversible, ice sheet change in West Antarctica. This session will convene speakers from the International Thwaites Glacier Collaboration, and welcomes contributions from studies that pertain to West Antarctic mass balance and future evolution of northern West Antarctica.

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Co-organized by CL4/OS1
Convener: Ted Scambos | Co-conveners: Karen J. Heywood, Kiya RivermanECSECS, David Vaughan
CL4.10

The earth's climate is highly variable on all spatial and temporal scales, and this has direct consequences for society. For example, changes in variability (spatial or temporal) can impact the recurrence frequency of extreme events. Yet, it is unclear if a warmer future is one with more, or with less, climate variability, and at which scales, as a multitude of feedbacks is involved, and the instrumental record is short.

We welcome contributions that improve quantification, understanding and prediction of climate variability in the Earth System across space and time scales through case studies, idealized or realistic modeling, synthesis, and model-data comparison studies that provide insights into past, present and future climate variability on local to global, and synoptic to orbital timescales. Members of the PAGES working group on Climate Variability Across Scales (CVAS) are welcome.

This session aims to provide a forum to present work on
• the characterization of climate dynamics using variety of techniques (e.g. scaling and multifractal techniques and models, recurrence plots or variance analyses) to study its variability including periodicities, noise levels, or intermittency.
• the relationship between changes in the mean state (e.g. glacial to interglacial, preindustrial to present to future), and higher-order moments of relevant climate variables, to changes in extreme event occurrence and the predictability of climate.
• the role of ocean, atmosphere, cryosphere and land surface processes in fostering long-term climate variability through linear – or nonlinear – feedbacks and mechanisms
• the attribution of climate variability to internal dynamics, or the response to natural (volcanic or solar) and anthropogenic forcing
• the interaction of external forcing (e.g. orbital forcing) and internal variability such as mechanisms for synchronization and pacing of glacial cycles.
• the characterization of probabilities of extremes, including rare “black swan” events and the linkage between slow (interannual to millennial) climate variability and extreme event recurrence
• the development and characterization of statistical tools and stochastic models to quantify the distribution, or scaling, of climate variability over a wide range of timescales from short, noisy and irregular (paleo-)climate time series, such as robust estimators for power spectral analyses, fluctuation analyses (detrended, Haar or other) and wavelets.

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Convener: Thomas Laepple | Co-conveners: Isabel de Lima, Raphaël HébertECSECS, Shaun Lovejoy, Kira Rehfeld
CL4.11

The large-scale atmospheric circulation strongly influences Earth's climate, both locally and globally, via its transport of energy, moisture, and momentum. While our ability to simulate the global circulation is improving, large model biases and uncertainties in climate change projections persist. Our theoretical understanding of how atmospheric circulations respond to climate changes is also limited, particularly on regional scales and in the presence of zonal asymmetries. Advancing our knowledge of the underlying dynamics is therefore crucial for reliable climate projections and for correctly interpreting palaeoclimate records.

The objective of this session is to advance our mechanistic understanding of atmospheric circulation changes and to analyse their impacts at global and regional scales, specifically on precipitation in past, present, and future climates. We encourage theoretical, observational and modelling contributions on tropical (ITCZ, monsoons, Hadley & Walker circulations, MJO) and extratropical circulations (jet streams, storm tracks, blocking).

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Co-organized by AS1
Convener: Michael ByrneECSECS | Co-conveners: Thomas Birner, Nicholas LutskoECSECS, Max Popp, Talia TamarinECSECS
CL4.12

Regional climate modeling has become an established and grwoing area of research in the last decades. Regional Climate Models (RCMs) are powerful and flexible tools which can be used for a wide variety of problems at regional scales, from the study of regional processes and the interactions between atmosphere, biosphere and chemosphere/aerosols to paleoclimate simulations and future climate projections. The resolution of RCMs varies from a few tens of km to convection-permitting scales (a few km) and the length of simulation has reached the multi-centennial scales. Different RCM intercomparison projects have been crried out in the past, culminating in the Coordinated Regional Downscaling EXperiment (CORDEX), an international program aimed at better understanding and improving regional downscaling techniques and producing large ensembles of projections for domains worldwide. The results from CORDEX and other RCM initiative have been extensively used for impact applications and provide the basis for many climate service activities. Following a tradition of very successful and well attended EGU sessions in the past, this session accepts frontier papers on all aspects of regional climate modeling science and application, and on the latest results from the CORDEX project.

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Convener: Filippo Giorgi | Co-conveners: Melissa Bukovsky, Ivan Guettler
CL4.13

One of the most striking features of global climate change is the strongly amplified response of surface air temperature in the Arctic and the associated strong decline in sea ice. Both observational and climate modeling studies have shown that the Arctic is a region very susceptible to climate change; moreover, changes occurring in the Arctic are likely to have more wide-spread implications. Arctic amplification manifests itself in a number of ways, most notably in the current retreat and thinning of Arctic sea ice. A variety of processes and feedbacks have been proposed that contribute to amplified Arctic warming, most of them associated with sea ice. The most well-known is the surface-albedo feedback, which is associated with retreating sea-ice and snow cover. While most climate models exhibit an Arctic amplification signal with respect to ongoing and future changes, the inter-model range in simulated amplification is large, suggesting that the magnitudes of the various feedbacks contributing to Arctic warming and the role of sea ice therein are still uncertain. This session specifically aims to identify, characterize and quantify the processes and feedbacks that govern amplified Arctic warming and sea ice retreat, and it also addresses the climate impacts on the lower latitudes associated with Arctic changes (for instance the relation between sea ice reductions, heat flux changes and atmospheric circulation changes beyond the Arctic region). We therefore invite contributions on the causes, mechanisms and climate feedbacks associated with Arctic climate change and sea ice decline, and the possible links to weather and climate outside the Arctic. We welcome studies based both on climate model results and/or observational datasets, for near-past, present and future climate changes.

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Co-organized by AS4/CR7
Convener: Richard Bintanja | Co-convener: Rune Grand Graversen
CL4.14

The Arctic Realm is changing rapidly and the fate of the cryosphere, including Arctic sea ice, glaciers and ice caps, is a source of concern. Whereas sea ice variations impact the radiative energy budget, thus playing a role in Arctic amplification, the Greenland Ice Sheet retreat contributes to global sea level rise. Moreover, through various processes linking the atmosphere, ice and ocean, the change in the Arctic realm may modify the atmospheric and ocean circulation at regional to global scales, the freshwater budget of the ocean and deep-water formation as well as the marine and terrestrial ecosystems. The processes and feedbacks involved operate on all time scales and thus require several types of information: satellite and instrumental data, climate models, and reconstructions based on geological archives. In this session, we invite contributions from a range of disciplines and across time scales, including observational data, historical data, proxy data, model simulations and forecasts, for the past, present and future climate. The common denominator of these studies will be their focus on a better understanding of mechanisms and feedbacks on short to long time scales that drive Arctic and subarctic changes and their impact on climate, ocean and environmental conditions, at regional to global scales, including possible links to weather and climate outside the Arctic.

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Co-organized by CR7/OS1
Convener: Marit-Solveig Seidenkrantz | Co-conveners: Anne de Vernal, Michal Kucera, Mimmi OksmanECSECS
CL4.15

The Arctic sea ice and high latitude atmosphere and oceans have experienced significant changes over the modern observational era. The polar climate is crucial for the Earth’s energy and water budget, and its variability and change have direct socio-economic and ecological impacts. Thus, understanding high-latitude variability and improving predictions of high latitude climate is highly important for society. Predictability studies indicate that decadal to multi-decadal variations in the oceans and sub-seasonal to multi-year sea ice variations are the largest sources of predictability in high latitudes. However, dynamical model predictions are not yet in the position to provide us with accurate predictions of the polar climate. Main reasons for this are the lack of observations in high latitudes, insufficient initialization methods and shortcomings of climate models in representing some of the important climate processes in high latitudes.
This session aims for a better understanding and better representation of the mechanisms that control high latitude climate variability and predictability in both hemispheres at sub-seasonal to multi-decadal time-scales in past, recent and future climates. Further, the session aims to discuss ongoing efforts to improve climate predictions at high latitudes at various time scales (as e.g. usage of additional observations for initialization, improved initialization methods, impact of higher resolution, improved parameterizations) and potential teleconnections of high latitude climate with lower latitude climate. We also aim to link polar climate variability and predictions to potential ecological and socio-economic impacts and encourage submissions on this topic.
This session offers the possibility to present results from the ongoing projects and research efforts on the topic of high-latitude climate variability and prediction, including, but not limited to WWRP Year of Polar Prediction (YOPP), NordForsk-project ARCPATH, and the H2020-projects APPLICATE, INTAROS, BlueAction, PRIMAVERA.

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Co-organized by AS4/OS1
Convener: Torben Koenigk | Co-conveners: Neven-Stjepan Fuckar, Yongqi Gao, Helge Goessling
CL4.16

The North Pacific’s sensitivity to forcing and feedbacks to background climate are an important, but largely open question in assessments of global climate, both in the modern and geological past. Enhanced knowledge of processes of past climate change is crucial to separate between natural and anthropogenic forcing, and to enhance the reliability of future climate projections. On a spatial scale, this region also comprises major oceanographic patterns including Boundary Current systems e.g., Kuroshio/Oyashio, or the Alaskan Stream and several frontal regions. In addition, complex exchange processes and interactions between the open North Pacific and its marginal seas from low to high latitudes create a spatially heterogenous region, with small-scale mixing and both temporal and spatial variations in the system at atmospheric, and oceanic surface, subsurface and deep levels.
We aim to provide a comprehensive collection of original contributions and syntheses that foster the dynamic and four-dimensional understanding of the evolution of climate and oceanic modes in the North Pacific, including links and teleconnections to low latitudes (e.g. West Pacific Warm Pool) and polar regions, as well as to global ocean circulation and climate patterns.
We welcome contributions across all time scales, from the geological past to present. Results may be based on instrumental or proxy data, as well as climate modelling. The session should advance our process-oriented understanding of the complex role of the North Pacific and its marginals seas in regulating biogeochemical cycles, ocean overturning circulation, and ocean-atmosphere carbon budgets. These past climate scenarios can be used to create a framework for the identification of potential thresholds in the current, warming Earth system.

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Co-organized by OS1
Convener: Xun GongECSECS | Co-conveners: Lester Lembke-JeneECSECS, Gerrit Lohmann, Xuefa Shi
CL4.17

Mountains cover approximately one quarter of the total land surface on the planet, and a significant fraction of the world’s population lives in their vicinity. Orography critically affects weather and climate processes at all scales and, in connection with factors such as land-cover heterogeneity, is responsible for high spatial variability in mountain weather and climate.

Due to this high complexity, monitoring and modeling the atmosphere and the other components of the climate system in mountain regions is challenging both at short (meteorological) and long (climatological) time-scales. This session is devoted to the better understanding of weather and climate processes in mountain and high-elevation areas around the globe, as well as their modification induced by global environmental change.

We welcome contributions describing the influence of mountains on the atmosphere on meteorological time-scales, including terrain-induced airflow, orographic precipitation, land-atmosphere exchange over mountains, forecasting and predictability of mountain weather. Furthermore we invite studies that investigate climate processes and climate change in mountain areas and its impacts on dependent systems, based on monitoring and modeling activities. Particularly welcome are contributions that merge various sources of information and reach across disciplinary borders (atmospheric, hydrological, cryospheric, ecological and social sciences). In this respect the session invites also contributions on outcomes of the WMO "High Mountain Summit" taking place in October 2019.

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Co-organized by AS1/CR7/NH1
Convener: Wolfgang Schöner | Co-conveners: Carolina Adler, Maria Vittoria Guarino, Elisa Palazzi, Stefano Serafin
CL4.18

The Hadley circulation, as a primary driver of climate in the tropics, has a profound impact on societies and environments in the tropical belt. The ITCZ located within the Hadley circulation delivers large amount of precipitation while the edges of the Hadley cells determine the extension of the equatorward transport of moisture and the location of Earth’s arid regions. While studies of the Hadley system often focuses on the global scale, there exists significant regional and zonal variations of the circulation and precipitation patterns (notably associated with monsoon and Walker circulations) which are more relevant to societies than the global changes.
Recent advances have emphasized energetic aspects as a useful framework to understand their mean state, variability, and evolution under climate changes. The strength of the cross-equatorial Hadley Circulation is related to the inter-hemispheric heat transport, which influences the global ocean-atmosphere energy budget, while at the local scale the intensity of low level mass convergence and precipitation (in the ITCZ and monsoon regions) with the net input at the top and bottom of the atmosphere.
This session is specifically focused on the tropical/subtropical atmospheric circulation and precipitation variability.
Contributions on diverse aspects, such as dynamics, trends, characteristics and variability of past, current and future Hadley/Walker/monsoon circulations and their impacts on environment and societies, connection between the regional and global scales and coupling with the ocean are encouraged.

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Co-organized by AS4
Convener: Roberta D'AgostinoECSECS | Co-conveners: David Ferreira, Piero Lionello
AS3.8 | PICO

The interactions between aerosols, climate, and weather are among the large uncertainties of current atmospheric research. Mineral dust is an important natural source of aerosol with significant implications on radiation, cloud microphysics, atmospheric chemistry and the carbon cycle via the fertilization of marine and terrestrial ecosystems.
In addition, properties of dust deposited in sediments and ice cores are important (paleo-)climate indicators.

This interdivision session is open to contributions dealing with:
(1) measurements of all aspects of the dust cycle (emission, transport, deposition, size distribution, particle characteristics) with in situ and remote sensing techniques,
(2) numerical simulations of dust on global and regional scales,
(3) meteorological conditions for dust storms, dust transport and deposition,
(4) interactions of dust with clouds and radiation,
(5) influence of dust on atmospheric chemistry,
(6) fertilization of ecosystems through dust deposition,
(7) any study using dust as a (paleo-)climate indicator including investigations of Loess, ice cores, lake sediments, ocean sediments and dunes.

We especially encourage to submit papers on the integration of different disciplines and/or modeling of past, present and future climates.

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Co-organized by BG1/CL4/GM8/SSP3, co-sponsored by ISAR
Convener: Jan-Berend Stuut | Co-conveners: Paola Formenti, Joanna Nield, Claire Ryder, Mingjin TangECSECS
CL4.20

ENSO and its interactions with other tropical basins are the dominant source of interannual climate variability in the tropics and across the globe. Understanding the dynamics, predictability, and impacts of ENSO and tropical basins interactions, and anticipating their future changes are thus of vital importance for society. This session invites contributions regarding all aspects of ENSO and tropical basins interactions, including: dynamics, multi-scale interactions; low frequency, decadal and paleo variability; theoretical approaches; ENSO diversity; global teleconnections; impacts on climate, society and ecosystems; seasonal forecasting and climate change projections of ENSO and its tropical basins interactions. Studies aimed at understanding ENSO and its tropical basins interactions in models of a range of complexity are especially welcomed, including analysis of CMIP model intercomparisons.

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Co-organized by AS1/NP2/OS1
Convener: Dietmar Dommenget | Co-conveners: Daniela Domeisen, Eric Guilyardi
CL4.21

Land–atmosphere interactions often play a decisive role in shaping climate extremes. As climate change continues to exacerbate the occurrence of extreme events, a key challenge is to unravel how land states regulate the occurrence of droughts, heatwaves, intense precipitation and other extreme events. This session focuses on how natural and managed land surface conditions (e.g., soil moisture, soil temperature, vegetation state, surface albedo, snow or frozen soil) interact with other components of the climate system – via water, heat and carbon exchanges – and how these interactions affect the state and evolution of the atmospheric boundary layer. Moreover, emphasis is placed on the role of these interactions in alleviating or aggravating the occurrence and impacts of extreme events. We welcome studies using field measurements, remote sensing observations, theory and modelling to analyse this interplay under past, present and/or future climates and at scales ranging from local to global but with emphasis on larger scales.

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Co-organized by AS2/HS13
Convener: Wim ThieryECSECS | Co-conveners: Gianpaolo Balsamo, Diego G. Miralles, Sonia Seneviratne, Ryan Teuling
SSP1.10

Africa is the world’s second largest continent, encompassing diverse ecosystems in numerous climate classifications, ranging from tropical forests to subarctic drylands on its highest mountain peaks. All these different environments underwent tremendous climatic fluctuations in the geological past, causing severe environmental changes. Further, Africa is one of the most vulnerable continents to future climate change, with widespread and till now uncertain impacts on African environments and society, as predicted by the recent IPCC report.
This session aims to convene studies about climate and environmental variabilities in Africa on various time scales, in past and future. The session will be open for studies from marine and continental records, using any kind of archive and proxy data, such as sedimentological records, tree rings, speleothems, ice cores, fossil pollen as well as modern monitoring data and modeling studies.

Keynote speaker:
Dr. Annette Hahn (MARUM, University of Bremen) will talk on:
Driving forces of southern African hydroclimate: integrating source to sink and multi-archive studies.

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Co-organized by CL4
Convener: Inka MeyerECSECS | Co-conveners: Verena E. FoersterECSECS, Annett Junginger
CL4.24

Adapting to climate change in the Mediterranean region represents a critical socio-economic and environmental challenge. Different levels of exposure and vulnerability as well as different projected changes characterize the Mediterranean region. Understanding the past, characterizing the present and modelling the future are therefore essential steps to estimate the risks, assess the impacts of climate change, and identify potential adaptation and mitigation strategies. This multidisciplinary MedCLIVAR session encourages contributions from a broad range of disciplines and topics, e.g. dealing with: dynamics and processes of the climate system; sectorial impacts of climate change; climate change adaptation and mitigation; innovative methods and approaches in climate science. The session focuses on all time scales from paleoclimate to future model projections as well as on all relevant socio-economic sectors.

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Convener: Andrea Toreti | Co-conveners: Ana BastosECSECS, Piero Lionello
ITS2.2/GM12.5

Documenting the diversity of human responses and adaptations to climate, landscapes, ecosystems, natural disasters and the changing natural resources availability in different regions of our planet, cross-disciplinary studies in Geoarchaeology provide valuable opportunities to learn from the past. Furthermore, human activity became a major player of global climatic and environmental change in the course of the late Quaternary, during the Anthropocene. Consequently, we must better understand the archaeological records and landscapes in context of human culture and the hydroclimate-environment nexus at different spatial and temporal scales. This session seeks related interdisciplinary papers and specific geoarchaeological case-studies that deploy various approaches and tools to address the reconstruction of former human-environmental interactions from the Palaeolithic period through the modern. Topics related to records of the Anthropocene from Earth and archaeological science perspectives are welcome. Furthermore, contributions may include (but are not limited to) insights about how people have coped with environmental disasters or abrupt changes in the past; defining sustainability thresholds for farming or resource exploitation; distinguishing the baseline natural and human contributions to environmental changes. Ultimately, we would like to understand how strategies of human resilience and innovation can inform our modern strategies for addressing the challenges of the emerging Anthropocene, a time frame dominated by human modulation of surface geomorphological processes and hydroclimate.

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