CL3.1.2 | Attribution in climate (impact) science: From long-term trends to extreme events and impacts
EDI
Attribution in climate (impact) science: From long-term trends to extreme events and impacts
Including Arne Richter Award for Outstanding Early Career Scientists Lecture
Convener: Sebastian Sippel | Co-conveners: Sabine Undorf, Aurélien Ribes, Veronika Huber, Sihan Li, Matthias Mengel, Nikolaos Christidis
Orals
| Tue, 25 Apr, 08:30–12:30 (CEST), 14:00–18:00 (CEST)
 
Room E2
Posters on site
| Attendance Wed, 26 Apr, 14:00–15:45 (CEST)
 
Hall X5
Posters virtual
| Attendance Wed, 26 Apr, 14:00–15:45 (CEST)
 
vHall CL
Orals |
Tue, 08:30
Wed, 14:00
Wed, 14:00
Attribution research assesses how anthropogenic and natural forcings may contribute to observed changes in the climate system as well as ensuing changes in natural, managed, and human systems. With regard to observed climatic trends, Detection and Attribution (DA) studies aim to identify historical changes over long timescales (typically multi-decadal), and quantify the contributions of various external forcings as their signal emerges above internal climate variability. Event attribution (EA) assesses how anthropogenic climate change may be modifying characteristics like the frequency and intensity of weather and climate extreme events. This rapidly evolving scientific area has introduced a range of methodologies and different ways of framing attribution questions. Impact attribution in turn aims to assess in a quantitative manner the contribution of anthropogenic climate change to observed changes in natural, managed, or human systems, extending existing concepts as well as calling for new approaches, given the added complexity from non-climatic human influences on many of these systems.
This session includes recent studies from the spectrum of DA research that address any or all steps of the forcing-climate-impact chain and aims to explore the diversity of methods employed across disciplines and schools of thought.
Trend and EA studies will consider a wide range of temporal and spatial scales. We thereby aim to identify common and new methods, including approaches based on statistical causality or AI, current challenges, and avenues for expanding the detection and attribution community. We particularly welcome submissions that compare approaches, address hydrometeorological trends, extremes, including compound/cascading events and/or assess implications of recent trends for constraining future changes – all of which test the limits of the present science.
We also welcome studies that go beyond climatic phenomena by attributing observed changes and events in natural, managed, and/or human systems. Examples include the attribution of observed socio-economic impacts (e.g., food price) via changes in the biophysical system (e.g., agricultural drought) driven by greenhouse gas emissions. Studies may also restrict their analysis to parts of the climate-impact chain, such as attributing an observed biophysical impact (e.g., species migration) to observed climate change.

Orals: Tue, 25 Apr | Room E2

Chairpersons: Sebastian Sippel, Aurélien Ribes
08:30–08:35
08:35–08:45
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EGU23-10927
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Virtual presentation
Surendra Rauniyar, Pandora Hope, and Scott Power

Rainfall across the state of Victoria in Australia exhibits a strong climatological gradient from north to south and from east to west. In general, the highland areas in eastern Victoria receive the highest rainfall, followed by the southern coastal regions and substantially less rainfall occurs over the north-west of Victoria. The latter two regions show a pronounced annual cycle with winter maxima while rainfall over eastern Victoria is more uniform throughout the year. These distinct variations in rainfall arise from the fact that the different regions of Victoria are influenced by different weather systems and large-scale climate drivers and they also respond differently to external forcing. Many of the previous studies on rainfall changes were derived using all-Victoria area-averaged rainfall. However, there is a strong interest of stakeholders, both within and beyond the climate science community in Australia, about the role of climate change on the decline in local rainfall since the beginning of the Millennium Drought in 1997.

In this study, we used both observations and climate models to provide comprehensive and robust information on past and future rainfall changes on three sub-regions of Victoria (Murray Basin Victoria: MBVic, southeast Victoria: SEVic, and southwest Victoria: SWVic) during the cool season (April – October) due to climate change. Our results show that the percentage decline of rainfall for the 1997-2018 period, relative to the 1900-1959 period average, is more pronounced over the MBVic and SEVic regions of Victoria and least pronounced over the SWVic region. However, the fractional contribution of external forcing is estimated to be about 30% to the observed drying over SWVic which is about 1.5 times higher than the other two regions. Equivalently, the external forcing contribution to the observed trend for the 1900-2018 period are 56%, 17% and 24% for SWVic, MBVic and SEVic, respectively. These numbers suggest that the recent drying across Victoria, while primarily driven by internal rainfall variability, was reinforced by external forcing.  We are currently investigating the time of emergence of the external forcing signal beyond its pre-industrial and historical range and the expected combined impact of both external forcing and internal variability on rainfall over different sub-regions of Victoria for coming decades.

How to cite: Rauniyar, S., Hope, P., and Power, S.: The role of external forcing and natural processes on past and future changes in rainfall over sub-regions of Victoria, Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10927, https://doi.org/10.5194/egusphere-egu23-10927, 2023.

08:45–08:55
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EGU23-8136
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ECS
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On-site presentation
Chen Lu, Gordon Huang, Xiuquan Wang, and Erika Coppola

It has been established that the variations/trends in large-scale precipitation over land since the mid-twentieth century can be attributed to forcing changes due to anthropogenic greenhouse gas emissions (Eyring et al.). The detection and attribution (D&A) of changes in regional precipitation regimes, however, remains challenging due to issues such as larger influences from internal variability, as well as larger uncertainty in observed and simulated data (Doblas-Reyes et al.). This study is aimed at exploring the feasibility of attributing the quantile trends in daily precipitation over China to natural and anthropogenic influences, aided by the latest CMIP6 GCM data. The quantile trends in observed and modeled daily precipitation are derived through quantile regression (Koenker and Bassett). The scenarios considered are the historical, natural, anthropogenic greenhouse gas, and anthropogenic aerosol forcings, and the control simulations are employed to reflect natural variability. The D&A is undertaken through the regularized optimal fingerprinting (Ribes et al.). The results show that the increasing trends in winter precipitation at high and extremely high quantile levels, as well as the increasing trends in spring precipitation at all quantile levels, can be attributed to the effects of historical forcing. The effect of anthropogenic greenhouse gas forcing is evident over the domain, to which the increasing precipitation trends at all quantile levels in all seasons can be attributed; this effect can be separated from that of anthropogenic aerosol forcing for winter precipitation trends at high and extremely high quantile levels, and for spring, summer, and autumn trends at low quantile levels. Findings of this research can help improve our knowledge of anthropogenic processes on the climate system, which can further support climate modeling and projections.

 

Reference

Doblas-Reyes, F. J., et al. “Linking Global to Regional Climate Change.” Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V. Masson-Delmotte et al., Cambridge University Press, 2021.

Eyring, V., et al. “Human Influence on the Climate System.” Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V. Masson-Delmotte et al., Cambridge University Press, 2021, pp. 423–552, https://doi.org/10.1017/9781009157896.005.

Koenker, Roger, and Gilbert Bassett. “Regression Quantiles.” Econometrica, vol. 46, no. 1, Jan. 1978, p. 33, https://doi.org/10.2307/1913643.

Ribes, Aurélien, et al. “Application of Regularised Optimal Fingerprinting to Attribution. Part I: Method, Properties and Idealised Analysis.” Climate Dynamics, vol. 41, no. 11–12, Dec. 2013, pp. 2817–36, https://doi.org/10.1007/s00382-013-1735-7.

How to cite: Lu, C., Huang, G., Wang, X., and Coppola, E.: Anthropogenic influence on precipitation quantile trends over China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8136, https://doi.org/10.5194/egusphere-egu23-8136, 2023.

08:55–09:05
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EGU23-16818
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ECS
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On-site presentation
Disha Sachan, Amita Kumari, and Pankaj Kumar

Climate change is leading to alterations in the dynamic climate systems worldwide. The Indian Summer Monsoon (ISM) is one such climate system that supports more than a billion population and drives the Indian economy. The ISM is governed by intra-annual to inter-decadal variabilities. However, anthropogenic climate change is inducing unprecedented transformations in this natural system, such as the increased probability of precipitation extremes (dry and wet), changes in their frequency and duration, spatial variabilities, etc. These changes, in turn, impact the human and ecological systems due to droughts, floods, and prolonged dry spells. In such scenarios, it is essential to gain insights into the projected precipitation extremes (PEs) changes. The velocity of climate change (VoCC) or climate velocity can help us project the temporal and spatial shift of PEs especially in terms of their intensities. VoCC is a regional metric of climate change, defined as the ratio of the temporal gradient of a particular climate variable (temperature, precipitation, humidity, etc.) with its spatial gradient, and the resultant units are in km/year. In the current study, the climate velocities of 50th, 75th, 95th, 99.5th, and 99.9th percentiles of precipitation for the JJAS season are projected over India and its different biogeographic zones for the four time periods: historical (1976-2000), near-future (2025-2049), mid-future (2050-2074) and far-future (2075-2099). ROM, a regional earth system model over the CORDEX-South Asia domain was used in the study. It was found that ROM showed a better resemblance with observation in simulating the PEs over other regional climate models (RCMs). The intense rainfall (95th percentile: R95) is expected to be enhanced over most of the study region in mid future and far future. Interestingly, very intense rainfall (99.9th percentile: R99) showed robust increases in the near and mid-future as compared to the far future. The PEs also exhibited higher velocities as compared to the median values. The detailed results will be discussed further in the presentation.

How to cite: Sachan, D., Kumari, A., and Kumar, P.: Shifting Velocity of Precipitation Extremes over India under Climate Change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16818, https://doi.org/10.5194/egusphere-egu23-16818, 2023.

09:05–09:15
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EGU23-4056
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On-site presentation
Detectable Human Influence on Changes in Precipitation Extremes across China
(withdrawn)
Huiwen Xu, Huopo Chen, and Huijun Wang
09:15–09:25
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EGU23-911
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ECS
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Virtual presentation
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Haosu Tang, Gang Huang, Kaiming Hu, and Jun Wang

Due to windward slope topography and monsoon activities, the populated Northeast Indian subcontinent (NEI) suffers from heavy rainfall and floods almost every year. Extreme persistent downpours lashed NEI in summer 2020, ranked the second heaviest on record since 1901. This event caused about 550 fatalities and economic loss up to hundreds of millions of dollars. It is highly compelling but challenging to understand the weather drivers and future risks of this high-impact event. Here, we suggested this event was likely caused by the anomalous anticyclone (AAC) over the Indo-Northwest Pacific region and La Niña-induced Walker circulation intensification. The overall effect of current human-induced climate change contributed little to the occurrence probability of this event, as most of the warming and wetting effects of greenhouse gases were canceled out by anthropogenic aerosols. Climate models project an increasing risk of 1.77 (1.97), 2.08 (2.59), 2.58 (3.88), and 3.10 (5.52) times of such extreme event in the median-term (long-term) future under SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5, respectively. It is mainly caused by the increases in atmospheric water vapor and 2020-like AAC frequency. Our findings indicate that future flooding risk over NEI will increase robustly if greenhouse warming continues.

How to cite: Tang, H., Huang, G., Hu, K., and Wang, J.: Increasing 2020-Like Boreal Summer Rainfall Extremes Over Northeast Indian Subcontinent Under Greenhouse Warming, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-911, https://doi.org/10.5194/egusphere-egu23-911, 2023.

09:25–09:35
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EGU23-13786
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ECS
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On-site presentation
Paula Gonzalez, Philippe Naveau, Soulivanh Thao, and Julien Worms

In the context of climate change, assessing how likely a particular change or event has been caused by human influence is important for mitigation and adaptation policies. Disturbances, such as increases in the frequency and intensity of extreme precipitation have been observed at continental to global scales. In this work we present an Extreme Event Attribution methodology for yearly maxima records that takes into consideration the temporal non-stationarity of climate variables and allow us to quantify record probability at a global scale in a transient setup. We apply our methodology to study records of yearly maxima of daily precipitation issued from the numerical climate model IPSL-CM6A-LR and the scenario rcp8.5 at a global scale. Focusing on decadal records, we detect a clear anthropogenic signal from the 2020's, even thought decadal record probability increases in most parts of the world, we observe a decrease of records probability in the subtropics.

How to cite: Gonzalez, P., Naveau, P., Thao, S., and Worms, J.: Analysis of precipitation records from climate models in a non-stationary context, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13786, https://doi.org/10.5194/egusphere-egu23-13786, 2023.

09:35–09:45
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EGU23-7148
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On-site presentation
Detection, attribution and specifying mechanisms of hydrological changes in geographically different river basins
(withdrawn)
Alexander Gelfan, Andrey Kalugin, and Inna Krylenko
09:45–09:55
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EGU23-5392
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On-site presentation
Hyungjun Kim and Nobuyuki Utsumi

The impact of climate change on typhoon is of great concern in the East Asia. In particular, typhoon heavy rainfall has a destructive impact on our society and economy since they are many megacities along the coastal regions. Although observations suggest significant changes in typhoon heavy rainfall, the contribution of anthropogenic forcing has not been determined.

In this study, we show that anthropogenic global warming has a substantial impact on the observed changes in typhoon heavy rainfall in the western North Pacific region. Observational data show that, in general, typhoon heavy rainfall has increased (decreased) in coastal East Asia (tropical western North Pacific) during latter half of 20th Century and onward. A similar spatial distribution is found in the “Anthropogenic fingerprint”, difference between Earth systems with and without human-induced greenhouse gas emission, from a set of large ensemble climate simulations. This provides evidence to support that the significant increase in the frequency of typhoon heavy rainfall along coastal East Asia is not explained solely by natural variability. Further, the results show that since mid-1970s, the signal of “Anthropogenic fingerprint” has been increasing rapidly and departs from natural variability in early-2000s.

Reference:
Utsumi, N., & Kim, H. (2022). Observed influence of anthropogenic climate change on tropical cyclone heavy rainfall. Nature Climate Change, 12(5), 436–440. https://doi.org/10.1038/s41558-022-01344-2

How to cite: Kim, H. and Utsumi, N.: Anthropogenic Fingerprint on Recent Changes in Typhoon Heavy Rainfall beyond Tipping-Point, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5392, https://doi.org/10.5194/egusphere-egu23-5392, 2023.

09:55–10:05
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EGU23-15502
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ECS
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On-site presentation
Lucas Fery, Bérengère Dubrulle, and Davide Faranda

A thunderstorm system formed during the night of August 17 to 18 over the northern Balearic Islands and moved rapidly to the northeast, causing widespread damage over Corsica, Northern Italy and Austria due to the production of strong surface wind gusts (>200 km/h over Corsica) and severe hail. The intensity of this phenomenon can be classified in the category of derechos: this is a classification of very violent storms that takes into account the wind gusts (more than 94km/h with maxima of more than 120km/h) and the extent of the affected territory (major axis longer than 400 kilometers). Here we analyse recent derechos event in France in the satellite era and assess the role of climate change in modifying their characteristics. We identify eleven events in the past and provide their tracks retrieved using the ERA5 reanalysis dataset. To detect climate change signal, we compare  analog cyclonic atmospheric circulations that can lead to derechos in the distant past (1950-1979) and in the recent past (1992-2022). Two of the events, the derechos which affect the Northern regions are unprecedented, that is no good analogues can be found and attribution statements cannot be made on the basis of the present analysis. For the other events, instead, we find a significant signal of increased precipitation in the recent period which, without change in circulation, is explained by the higher temperatures of the Bay of Biscay and the Mediterranean Sea. For these events there is also not a clear change in depth of the pressure minimum which triggered the convective system. Finally, we can exclude the role of the climate variability of El Nino (ENSO) in most of the events, while we cannot rule out the influence of the Atlantic Multidecadal Oscillation (AMO) in favoring low pressure systems possibly leading to derechos.

How to cite: Fery, L., Dubrulle, B., and Faranda, D.: Climate change has increased the intensity of documented Derecho storms in France, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15502, https://doi.org/10.5194/egusphere-egu23-15502, 2023.

10:05–10:15
Coffee break
Chairpersons: Aurélien Ribes, Sebastian Sippel
10:45–10:50
10:50–11:10
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EGU23-11732
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solicited
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Highlight
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On-site presentation
Erich Fischer

Parts of western North America experienced a heatwave in late June 2021that many would have conceived impossible based on observations so far. In Lytton, Canada, temperatures peaked at 49.6°C, and the area-average daily maximum temperature record across the Pacific Northwest was broken by nearly 5°C. Given the exceptional intensity of the eventsome media outlets and scientists raised the questions whether heat extremes intensify faster than previously projected based on climate models, or whether current generations of climate models miss crucial processes and are thus unable to even reproduce such an event.. Here I address these questions and highlight some of the challenges for widely methods in model evaluation and attribution.

First, I review some of the recent literature detailing the key physical mechanisms driving the Pacific Northwest heatwave. I address some of the key scientific challenges regarding the quantification of return periods, event attribution, model evaluation and near-term projections. Widely used methods estimating stationary return periods based on the observational record up to the year before imply that such an event had an infinite return period, i.e., that it would never happen. Even when taking into account the non-stationarity of a warming climate, the exceedance probability would be zeroor nearly zero depending on the estimation of the confidence intervals, the duration of the event and whether the event itself is included in the fit.

I discuss some potential ways forward in addressing the above challenges and in quantifying the potential intensity of record-shattering events in the near future.  

How to cite: Fischer, E.: The record-shattering 2021 Pacific Northwest heatwave – challenges and opportunities for attribution and event storylines, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11732, https://doi.org/10.5194/egusphere-egu23-11732, 2023.

11:10–11:20
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EGU23-233
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ECS
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Highlight
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On-site presentation
Camille Cadiou and Pascal Yiou

Extreme winter cold temperatures in Europe have huge societal impacts. Being able to simulate worst-case scenarios of such events for present and future climates is hence crucial for adaptation. Rare event algorithms have been applied to simulate extreme heat waves. They have emphasized the role of atmospheric circulation in such extremes. The goal of this study is to test such algorithms for extreme cold spells.

We focus first on winter cold temperatures that have occurred in France from 1950 to 2021 and then on winter cold spells that could occur in the future according to different emissions pathways. We investigate winter mean temperatures in France (December, January, and February) and identify a record-shattering event in 1963. We find that, although the frequency of extreme cold spells decreases with time, their intensity is stationary.

We applied a stochastic weather generator approach with importance sampling, to simulate the coldest winters that could occur every year since 1950. We hence simulated ensembles of worst winter cold spells that are consistent with observations. Only some of the simulations reach colder temperatures than the record-shattering event of 1963, and the ensembles do not yield the trend that is observed in the mean temperature. The atmospheric circulation that prevails during those events is analyzed and compared to the observed circulation during the record-breaking events.

How to cite: Cadiou, C. and Yiou, P.: Simulating extreme cold winters in France with empirical importance sampling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-233, https://doi.org/10.5194/egusphere-egu23-233, 2023.

11:20–11:30
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EGU23-16087
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Highlight
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On-site presentation
Neven Fuckar, Myles Allen, and Michael Obersteiner

As climate changes to likely a warmer mean state by the end of this century than any time during the existence of humans, the world population has rapidly increased from about 1.3 billion in 1850 to 8 billion in November 2022. The latest IPCC AR6 reports attests that extreme events (e.g., heatwaves, floods, droughts, etc.) are occurring in many parts of the world at an increasing frequency and/or intensity due to global climate change, and are threatening human health, Earth’s biosphere, and the socio‐economic fabric of our rapidly expanding and resource‐hungry civilisation. On 19 July 2022 England, Wales and Scotland all experienced the hottest days on the record reaching 40.3 deg.C, 37.1 deg.C and 34.8 deg.C, respectively, and London Fire Brigade received the highest number of emergency calls since World War II. While in Dublin near-surface air temperature reached 33.0 deg.C on 18 July – the highest in the Ireland’s record. Furthermore, the annual mean temperature in 2022 was highest on the record in the UK and Ireland. This study uses a set of observations and reanalysis products combined with large ensembles of CMIP5/6 simulations to examine the structure of atmospheric circulation and the role of anthropogenic drivers leading to these extreme events on annual timescale. We also use large ensembles of specifically designed historical/factual and natural/counterfactual simulations of EC-Earth3 coupled climate model at the standard resolution and weather@home2 climate simulations performed by citizen scientists around the world to assesses to what extent anthropogenic forcing modified the probability and magnitude of this event. Moreover, we involve conditional perspective of the atmospheric circulation in our attribution estimates. The preliminary results points to a pronounced role of the global climate change in modifying likelihood and intensity of these annual extreme events.

How to cite: Fuckar, N., Allen, M., and Obersteiner, M.: On the nature and attribution of the 2022 annual record temperature in the UK and Ireland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16087, https://doi.org/10.5194/egusphere-egu23-16087, 2023.

11:30–11:40
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EGU23-13745
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Highlight
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On-site presentation
Julien Cattiaux and Aurélien Ribes

Because they are rare, extreme weather events inevitably attract public and scientific attention. The most unusual events are regularly documented as part of routine climate monitoring by meteorological services, and put into the perspective of climate change by attribution studies through quantities such as a probability ratio. However, it is often recognized that (i) the selection of studied events is geographically uneven, and (ii) the definition of a given event, in particular its spatio-temporal scale, is subjective, which may impact the results.

In previous work, we proposed an objective method of event definition, consisting in the automatic selection of the spatio-temporal window maximizing the event rarity. Importantly, we showed that maximizing the event rarity does not bias attribution statements, in the sense that it does not systematically maximize (or minimize) the probability ratio. Here we present how this method can be used to compare several events occurring on different years, seasons, regions, etc. Our objective research procedure works both over time, which can be useful for routine climate monitoring, and over space, which can resolve the geographical selection bias of attribution studies. Ultimately, we provide a selection of the most extreme hot and cold events that have occurred worldwide in the recent past, among which are iconic heat waves such as that seen in 2021 in Canada or 2003 in Europe.

How to cite: Cattiaux, J. and Ribes, A.: Searching for the most extreme temperature events in recent history, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13745, https://doi.org/10.5194/egusphere-egu23-13745, 2023.

11:40–11:50
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EGU23-3235
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On-site presentation
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Joel Zeder, Sebastian Sippel, and Erich Fischer

Primer: The record-shattering Pacific Northwest heatwave in late June 2021 challenged a key element of extreme event attribution, namely, the statistical evaluation of the event likelihood given historical records up to the event. The respective model, a non-stationary generalised extreme value (GEV) distribution depending on a global mean temperature covariate, suggested an infinite return period, or zero probability of reaching the event intensity in the year in which it was observed, based on the historical record. The apparent shortcoming of the method triggered a widespread debate about the general suitability of this statistical approach and its ability to provide informative insight in the context of extreme event attribution.

Research objective: The aim of this study is to first evaluate the quality of return period estimates for very rare heatwave events to determine whether or not the method can reliably characterise the event likelihood of rare extremes. We then assess the contributions of different factors to systematic deviations in tail estimates (such as high quantiles or return periods) relevant for rare event attribution statements. We consider both aspects associated with the statistical method, as well as such related to the attribution procedure.

Data & Methods: A robust evaluation of tail estimates requires vast amounts of homogeneous data. Our analysis is based on two transient historical and future (RCP8.5 and SSP3.7) initial condition large ensembles (84 and 100 members) and an extensive bootstrap dataset of extreme values simulated from parametric GEV distributions.

Results: We demonstrate that also in climate model experiments, events analogous to the 2021 heatwave are simulated, which, assessed with data up to the event, would have deemed to have zero occurrence probability. Thus, also within the climate model context, we find that the non-stationary GEV approach yields substantially biased exceedance probability estimates for low-likelihood events, thereby overestimating the respective return period or underestimating the likelihood of occurrence if the GEV distribution is based on a relatively short “historical” record. This systematic has become particularly pronounced in recent extreme events due to the emergence of a distinct climate change signal and high rate of warming.

Especially maximum likelihood estimates of the non-stationary GEV distribution are prone to systematically underestimate the shape parameter, and in consequence overestimate the return periods. We demonstrate that the bias arises because the GEV fit is restricted to rather short time series, and it is partially alleviated if a Bayesian estimation approach is used. Furthermore, widely used symmetric, so-called Wald-type maximum likelihood confidence intervals are found to be a rather inadequate and misleading measure of the estimation uncertainty in GEV-parameters and tail quantities like return levels. For these reasons, Wald-type confidence intervals should thus not be used for model evaluation purposes in extreme event attribution studies.

How to cite: Zeder, J., Sippel, S., and Fischer, E.: Are return period estimates from observational records reliable for low-likelihood heatwave events? A systematic evaluation, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3235, https://doi.org/10.5194/egusphere-egu23-3235, 2023.

11:50–12:00
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EGU23-11234
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ECS
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On-site presentation
Marc Lemus-Canovas, Sergi Gonzalez-Herrero, Laura Trapero, Anna Albalat, Damian Insua-Costa, Martin Senande-Rivera, and Gonzalo Miguez-Macho

The field of extreme event attribution (EEA) seeks to quantify how recent extreme events are directly exacerbated by ongoing climate change. As this is a relatively new field in climate science, there is a noticeable knowledge gap in EEA analysis in mountain areas. Precisely, this work performs an attribution to climate change of the two greatest heatwaves (HWs) occurred during June and July 2022, both hitting the Iberian Peninsula and southern France, and therefore, the Pyrenees Mountain range. We used the analogues technique on 500 hPa geopotential height composites to identify the 30 days closer to the dynamical structure of both heatwaves for the counterfactual (1950-1985) and factual (1986-2021) period, using ERA5 daily data. Results showed that factual HWs analogues in the factual period have a spatial structure closer to the 2022 HWs events than those analogues extracted from the counterfactual period. At the Pyrenean scale, we observed that 2-meter air temperature differences consisted of a positive non-uniform pattern in a factual world, with a significant increase in the southern slope of the mountain range and in the nearby depressed areas. However, most of the mountain range exhibited a small increase of the HW air temperature in a factual world. We also provided an explanation of the physical process involving the abovementioned 2-meter air temperature differences. In this study, we revealed the complexity of conducting the attribution of extreme heatwaves to climate change in mountain areas, both because of the scarcity of in-situ data, as well as due to the physical processes involved during these extreme events in an area of complex terrain.

How to cite: Lemus-Canovas, M., Gonzalez-Herrero, S., Trapero, L., Albalat, A., Insua-Costa, D., Senande-Rivera, M., and Miguez-Macho, G.: Attributing heatwaves to climate change in mountainous areas. An analysis of the summer 2022 heatwaves in the Pyrenees, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11234, https://doi.org/10.5194/egusphere-egu23-11234, 2023.

12:00–12:10
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EGU23-12990
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On-site presentation
Jitendra Singh, Sebastian Sippel, and Erich Fischer

Heat extremes show the fastest warming trend over western Europe (WEU) and a weak cooling trend over the Midwest United States (MUS). We use observations and Earth System Model (ESM) large ensemble simulations to understand why the observed trends over these two regions are opposite. Based on the dynamical adjustment method we provide observational and model evidence that circulation changes greatly amplify the warming trends over WEU and weaken the trends over MUS in the last four decades. We find that circulation-driven changes in heat extremes cause ~0.2°C/decade cooling over MUS that reverses the weaker warming effects of all other forcings combined and thus leads to very small overall trends. In contrast, it causes an additional ~0.2°C/decade warming over WEU, which accounts for ~35% of the warming rate that is caused by forced thermodynamic changes. Although ESMs represent the forced thermodynamic warming well over WEU, they underestimate the circulation-induced warming that further reveals why ESMs underestimate the observed warming rate over WEU.

Overall, these findings imply that if the circulation changes represent a forced response WEU continues to experience a severe intensification of heat extremes conditions in future as circulation-induced amplification of heat extremes may further intensify in the warmer world. Conversely, if the circulation-induced trend were due to internal variability, and thus would reverse in the coming decades, this would imply a somewhat slower rate of warming of heat extremes. Moreover, heat extremes over MUS continue to warm more slowly if circulation keeps dampening the warming effects in the coming decades, but potentially increase rapidly if the circulation trend reverses.

How to cite: Singh, J., Sippel, S., and Fischer, E.: Observed intensification of heat extremes amplified by circulation over western Europe and dampened over the US Midwest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12990, https://doi.org/10.5194/egusphere-egu23-12990, 2023.

12:10–12:20
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EGU23-1722
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ECS
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Virtual presentation
Nikhil Kumar and Manish Kumar Goyal

The intensification of the global hydrological cycle has significantly altered the behaviour of climate extremes. Lately, compound extremes i.e. simultaneous occurrence of two or more extremes, have received substantial emphasis because of their larger impact than individual extremes. Therefore, this study evaluates compound dry-hot extremes in summer monsoon season in India for the past and future using advanced statistical (variance transform method and REA- reliability ensemble averaging) and probabilistic methods (copulas). Monthly projections of precipitation/temperature are obtained from multi-modal ensembles of 21 CMIP5 GCMs, constructed using the REA technique. Furthermore, the frequency and spatial extent of monsoonal compound dry-hot events are assessed using a Standardized Compound Event Indicator (SCEI), based on monthly precipitation/temperature, for past (1975-2015)  and future (2025-2095 under RCP8.5). Moreover, vegetation loss estimates (using NDVI-Normalized Difference Vegetation Index) are evaluated under multiple dry-hot conditions (using SCEI) during 1982-2013 using bivariate copulas. Further, the teleconnections (Nino3.4, PDO, AMO and DMI) with SCEI are assessed using the variance transformation method. The results indicate a rise in dry-hot extremes in the monsoon season during 1975-2015. Due to the adverse impact of such extremes on vegetation, vegetation vulnerability assessment indicate that around 65.70% of the country’s area is prone to vegetation loss under extreme dry-hot conditions. And, it is also found that Nino3.4 (ENSO) is the dominant climate indice influencing SCEI (4 monthly scale), in > 50% of the country. Furthermore, the results show that the frequency and spatial extent of dry-hot extremes are projected to increase in the future (2055-2095), relative to past (1975-2015) across the country. Our study gives an enhanced understanding of dry-hot extremes in monsoon season and can further facilitate an effective adaptation strategy.

How to cite: Kumar, N. and Kumar Goyal, M.: Evaluation of compound dry-hot extremes in summer monsoon in India: Past and Future, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1722, https://doi.org/10.5194/egusphere-egu23-1722, 2023.

12:20–12:30
Lunch break
Chairpersons: Veronika Huber, Sihan Li, Sabine Undorf
14:00–14:05
14:05–14:25
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EGU23-5612
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ECS
|
solicited
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Highlight
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On-site presentation
Eunice Lo, Dann Mitchell, Ana M. Vicedo-Cabrera, and Sarah Perkins-Kirkpatrick

Attributing extreme weather events to human-induced climate change has been a topic of interest for decades. In recent years where unprecedented and high-impact events have occurred all over the world, it is all the more important to not just understand how human influence on the climate system has changed the probability or magnitude of the weather events, but also how it has changed the impacts of these events on human life. In this talk, I will review the climate-epidemiology literature on attributing adverse human health impacts to climate change, with a focus on heat-related mortality, as it is well-established that high temperatures are associated with increased mortality risks. I will include notable heat-mortality events in history such as the 1995 Chicago heatwave, 2006 UK summer, and the 2003 European heatwave. I will also discuss the use of large ensembles of future climate projections to ‘attribute’ heat-related mortality that could occur if global mean warming reached certain levels, keeping other factors unchanged. Finally, I will discuss the use of climate-health attribution information in engaging with the media and communicating with policymakers.

How to cite: Lo, E., Mitchell, D., Vicedo-Cabrera, A. M., and Perkins-Kirkpatrick, S.: Attributing human health impacts to climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5612, https://doi.org/10.5194/egusphere-egu23-5612, 2023.

14:25–14:35
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EGU23-6412
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On-site presentation
Philipp Aglas-Leitner, Sarah Perkins-Kirkpatrick, Nina Lansbury, Linda Selvey, Nicholas Osborne, and Daithi Stone

In recent decades, anthropogenic climate change has led to significant increases in heat wave length and intensity. Many of these heat waves have resulted in substantial impacts on human health. In 2009, the state of Victoria, Australia, experienced several days with maximum temperatures rising 12-15°C above the climatological mean and a marked rise in the human death toll. This study attempts to directly quantify the heat-related human fatalities of the 2009 heatwave attributable to anthropogenic climate change.

We focus on changes in return values of heat wave-related mortality. Furthermore, we combine two types of modeling tools. The first is a set of large initial-condition ensembles of simulations from atmosphere-only models from the weather@home/ANZ and C202C+ D&A projects, and large initial-condition ensembles of simulations from atmosphere-ocean models from CMIP6.  We compare factual outcomes from year-2009 era periods from historical simulations against counterfactual outcomes from either naturalised (non-anthropogenic) simulations or pre-industrial times. The second tool is an empirical model linking heat-related mortality to exceedance of temperature percentile thresholds from daily climate simulation output. This mortality model categorizes heat waves based on three consecutive percentile windows starting at the 95th, 97.5th, and the 99th percentile.

Our analysis shows considerable agreement among the climate-mortality model combinations indicating significant increases in human fatalities during conditions comparable to the 2009 Victoria heat wave under anthropogenic climate change. Most models attribute approximately one third to one half of excess heat-related deaths to anthropogenic greenhouse gas emissions. These findings demonstrate that unless significant climate change mitigation and adaptation efforts are undertaken, further increases in heat-related mortality risk can be expected.

How to cite: Aglas-Leitner, P., Perkins-Kirkpatrick, S., Lansbury, N., Selvey, L., Osborne, N., and Stone, D.: Attribution of excess heat-related death toll during 2009 heat wave in Victoria, Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6412, https://doi.org/10.5194/egusphere-egu23-6412, 2023.

14:35–14:45
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EGU23-14521
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ECS
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On-site presentation
Thessa Beck, Lukas Gudmundsson, Sonia I. Seneviratne, Hicham Achebak, Dominik Schumacher, and Joan Ballester

Extreme Event Attribution (EEA) aims to answer the question of whether and to what extent the intensity and likelihood of an observed extreme weather event have changed due to climate change. This approach has been applied to different types of weather extremes such as heatwaves, droughts, or extreme rainfall, but has only rarely been used to assess the role of climate change on health impacts caused by extreme weather events.

In this study, we focus on the short-term effects of extreme heat events on human mortality in Europe. We first apply an epidemiological model to estimate the lagged association between temperatures and mortality counts. We use ERA5-Land temperature data and a mortality database including 92.612.620 counts of death from 823 contiguous regions in 35 European countries, representing a population of over 534 million people. We estimate the number of deaths attributable to heat and then compute the death count caused by climate change by applying EEA methods. Here, we apply a conditional extreme value distribution to estimate how the likelihood of selected heat-attributable mortality events has changed from a pre-industrial climate to present-day conditions (1.2ºC global warming).

We show that in all regions of Europe, a climate change signal in heat-attributable mortality can be detected. This climate change contribution to mortality differs between geographical locations in Europe and is also influenced by demographic, and socioeconomic factors, e.g., we identify differences in climate impacts in gender-specific mortality.

This study shows that epidemiological models can be combined with EEA methodologies and it opens the door to conducting further EEA studies, including rapid attribution, on other health impacts and beyond.

How to cite: Beck, T., Gudmundsson, L., Seneviratne, S. I., Achebak, H., Schumacher, D., and Ballester, J.: Quantifying the contribution of climate change to heat-attributable mortality in Europe: Interfacing epidemiology and Extreme Event Attribution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14521, https://doi.org/10.5194/egusphere-egu23-14521, 2023.

14:45–14:55
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EGU23-17514
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On-site presentation
Felipe J Colón-González, Isabel Fletcher, Grace Annan-Callcott, and Bilal Mateen

There are valid concerns as to whether climate change has influenced the observed shifts in the spatial range, frequency, intensity, and duration of some health hazards. In a few cases, it has been possible to quantify the extent of this influence. However, current research is limited to a small number of health hazards and a handful of geographical areas, primarily in high income countries. This situation negatively affects the credibility of the mitigation policy arguments and constrains our ability to communicate with relevant stakeholders who might see climate impacts on health as distant in time, geography, or social cohort.  

Attribution science could be used to strengthen the evidence on how some types of health events have changed and how they are expected to change due to climate change. This evidence could be used as a case for limiting warming before irreversible changes occur. It will also be useful to inform adaptation strategies and increase the likelihood that policymakers will implement their announced climate change pledges and policies in a timely manner. 

Given its relatively new application to health, there are no clear best methods, sets of assumptions, or comprehensive data sets that could be used to attribute climate impacts on health. Also, the tools and methods for attributing climate impacts on health that exist in the literature tend to be created locally by a handful of institutions for a narrow use case and are often not easily reproducible.  Here, we present a funding organisation perspective on how we can start addressing some of the challenges on the D&A space.

How to cite: Colón-González, F. J., Fletcher, I., Annan-Callcott, G., and Mateen, B.: Challenges and opportunities for detection and attribution of climate change impacts on health, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17514, https://doi.org/10.5194/egusphere-egu23-17514, 2023.

14:55–15:05
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EGU23-17253
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ECS
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Virtual presentation
Asya Dimitrova, Anna Dimitrova, Matthias Mengel, Antonio Gasparrini, Sabine Gabrysch, and Hermann Lotze-Campen

Climate change is increasingly affecting the health of vulnerable populations, including pregnant women, the developing foetus and newborns. Despite growing epidemiological evidence on the effects of ambient temperatures on adverse birth outcomes and child survival, the role of climate change in the burden of temperature-related adverse birth outcomes has been insufficiently investigated. We combine data from the Demographic Health Survey (DHS) for 29 low- and middle-income countries with factual temperature data from the ISIMIP3a simulation round to quantify the non-linear association between daily mean temperature and stillbirths and neonatal deaths. We estimate the associations using a time-stratified case-crossover design. Based on the derived exposure-response functions and counterfactual temperature data we estimate the burden of stillbirths and neonatal deaths between 2001-2019 that can be attributed to climate change. The results both for stillbirths and neonatal deaths indicate a U-shaped curve, with risk of mortality increasing below and above an optimum temperature. We find that climate change has increased the burden of heat-related stillbirths across 28 of the countries (from 0.6% in Albania and Tajikistan to 4.1% in Philippines) and the burden of heat-related neonatal deaths – across 20 of the countries (from 0.2% in India to 1% in Philippines and Haiti). For 21 of the included countries climate change has also led to a reduction in the burden of cold-related stillbirths (from 0.2% in Tajikistan to 4.4% in Uganda) and neonatal deaths (from 0.5% in Tajikistan to 3.5% in the Philippines).

How to cite: Dimitrova, A., Dimitrova, A., Mengel, M., Gasparrini, A., Gabrysch, S., and Lotze-Campen, H.: The burden of temperature-related stillbirths and neonatal deaths attributable to climate change – a global analysis across 29 Low- and Middle-income countries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17253, https://doi.org/10.5194/egusphere-egu23-17253, 2023.

15:05–15:15
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EGU23-7528
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ECS
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On-site presentation
Rosa Pietroiusti and Wim Thiery

Heatwaves are increasing in frequency, intensity, and duration, and represent the category of extreme event that is most easily attributable to anthropogenic warming. Yet how the spatiotemporal patterns of attribution outcomes link to population dynamics is still poorly understood.  Here we show that children and young people are already being affected by a disproportionately greater number of attributable heatwaves, especially in the Global South. Using observations, reanalysis, and simulations of temperature changes available through the ISIMIP3b and CMIP6 projects in combination with demographic data, we show that temperature extremes emerge more clearly and consistently from the noise across low-income countries in lower latitudes, which have some of the youngest populations. Our findings have important implications for children and young people seeking redress from climate harms, for example through climate lawsuits.

How to cite: Pietroiusti, R. and Thiery, W.: Children disproportionally exposed to attributable heatwaves at low-latitude low-income countries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7528, https://doi.org/10.5194/egusphere-egu23-7528, 2023.

15:15–15:25
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EGU23-7716
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ECS
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On-site presentation
Luke Grant, Wim Thiery, Inne Vanderkelen, Lukas Gudmundsson, Erich Fischer, and Sonia Seneviratne

In climate change attribution, unprecedented magnitudes of extreme events can be defined on the basis of thresholds in the pre-industrial distributions of event magnitudes. This notion of unprecedented levels of climate change impacts has been extended toward the lifetime exposure to extreme events by evaluating exposure frequency. Unprecedented exposure to extreme events is assessed by comparing average lifetime exposure under different climate scenarios to an upper percentile of exposure in a pre-industrial climate. Here we combine simulations of climate change impacts under different climate forcing scenarios with country-level demography datasets to estimate the fraction of the global population experiencing unprecedented exposure to extreme events. This is done for 29 global mean temperature trajectories taken from the AR6 scenario explorer and multiple extreme event categories such as heatwaves, floods and droughts. Further, we assess the age of emergence at which birth cohorts reach unprecedented levels of exposure.

How to cite: Grant, L., Thiery, W., Vanderkelen, I., Gudmundsson, L., Fischer, E., and Seneviratne, S.: The evolution of the global population experiencing unprecedented exposure and its age of emergence., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7716, https://doi.org/10.5194/egusphere-egu23-7716, 2023.

15:25–15:35
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EGU23-1279
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On-site presentation
Gottfried Kirchengast, Stephanie Haas, and Jürgen Fuchsberger

Weather and climate extreme indicators are useful tools in the assessment and quantification of climate change induced alterations of key climate variables and extreme events. However, capturing both the main change aspects and the total extremity of such extreme events remains a challenging task.

Climate change can affect multiple characteristics of weather and climate extremes. Most indices, such as annual maximum temperature or number of hot days, focus on only one aspect of extreme events. While annual maximum temperature aims at describing the magnitude, the number of hot days is used for assessing the frequency of an extreme. The consideration of only one characteristic is a common limitation of such metrics. Since the total severity of extremes is the result of a combination of frequency, duration, magnitude and areal extent changes, however, the extremity is more than the sum of these parts and compound indices are hence required to fully capture the overall change.

Here we introduce Threshold-Exceedance-Amount (TEA) indicators as a new class of metrics that capture changes in event frequency, duration, magnitude, and spatial extent both in isolation and in total. Using a high-percentile-based threshold in a key climate variable that describes extreme magnitudes, the TEA metrics work in a cascaded manner up to expressing the total extremity of events, optionally also as an amplification vs. a suitable reference period.

Besides a detailed definition, we also show example applications for heat and heavy precipitation extremes (using daily maximum temperature and precipitation amount as key variables), from local- to country-scale regions in Austria to resolving and covering the entire European land region. We discuss amplifications and climate change detection vs. the 1961-1990 reference period and natural variability.

The TEA indicators are applicable for different types of extremes also beyond temperature and precipitation, making them a useful and versatile tool for the climate change-related investigation of extreme events and their impacts on natural and socio-economic systems, while also helping to fulfill the need for compound indices.

How to cite: Kirchengast, G., Haas, S., and Fuchsberger, J.: New Compound Extreme Event Indicators for Detecting and Tracking Weather and Climate Extremes under Climate Change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1279, https://doi.org/10.5194/egusphere-egu23-1279, 2023.

15:35–15:45
Coffee break
Chairpersons: Sabine Undorf, Sihan Li, Matthias Mengel
16:15–16:20
16:20–16:50
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EGU23-12474
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ECS
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solicited
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Arne Richter Award for Outstanding Early Career Scientists Lecture
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On-site presentation
|
Wim Thiery

Under continued global warming, extreme events such as heatwaves will continue to rise in frequency, intensity, duration, and spatial extent over the next decades. Younger generations are therefore expected to face more such events across their lifetimes compared to older generations. This raises important questions about solidarity and fairness across generations that have fuelled a surge of climate protests led by young people in recent years, and that underpin questions of intergenerational equity raised in recent climate litigation. However, scientific analyses that explicitly consider the intergenerational equity dimension of the climate crisis are remarkably absent. Our standard scientific paradigm is to assess climate change in discrete time windows or at discrete levels of warming, a “period” approach that inhibits quantification of how much more extreme events a particular generation will experience over its lifetime compared to another. By developing a “cohort” perspective to quantify changes in lifetime exposure to climate extremes and compare across generations, we estimate that children born in 2020 will experience a two to sevenfold increase in extreme events, relative to the 1960 birth cohort, under current climate pledges. Building on this framework, we quantify where and when people start living an unprecedented life, as well as intergenerational differences in exposure to attributable extreme events. Furthermore, using a new water deficit indicator, we uncover spatiotemporal differences in lifetime water scarcity. Our results overall highlight a severe threat to the safety of young generations and call for drastic emission reductions to safeguard their future. Finally, this research is already being used in ongoing litigation (e.g. Duarte Agostinho and Others v. Portugal and 32 Other States), calling for more research in this direction to bolster the upcoming wave of climate lawsuits.

How to cite: Thiery, W.: The kids aren’t alright, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12474, https://doi.org/10.5194/egusphere-egu23-12474, 2023.

16:50–17:00
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EGU23-14756
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ECS
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Highlight
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On-site presentation
Seppe Lampe, Chantelle Burton, Eleanor Burke, Jinfeng Chang, Nikos Christidis, Matthew Forrest, Lukas Gudmundsson, Huilin Huang, Stijn Hantson, Akihiko Ito, Douglas Kelley, Sian Kou-Giesbrecht, Gitta Lasslop, Fang Li, Wei Li, Lars Nieradzik, and Wim Thiery

Recent long and intensive wildfire seasons in many regions have highlighted the urgency to understand the shift in worldwide fire regimes, raising the question if human induced climate change has played a role therein. However, attributing changes in fire to anthropogenic climate change is difficult, since possible signals are confounded by multiple drivers including fire weather, fuel availability and sources of ignition. Therefore, fire indices or individual input variables are often used as proxies. There have been some attempts to model drivers of recent trends in fire, though assessment of overall anthropogenic climate change is still lacking. Recent integration of fire models into ISIMIP now allow us to perform a fire impact attribution analysis using multiple coupled fire-vegetation models. Here, we combine both ISIMIP factual and counterfactual simulations with remote sensed observations to understand how burnt area has changed over the historical period due to a changing climate.

How to cite: Lampe, S., Burton, C., Burke, E., Chang, J., Christidis, N., Forrest, M., Gudmundsson, L., Huang, H., Hantson, S., Ito, A., Kelley, D., Kou-Giesbrecht, S., Lasslop, G., Li, F., Li, W., Nieradzik, L., and Thiery, W.: The Effect of Climate Change on Global Wildfire Activity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14756, https://doi.org/10.5194/egusphere-egu23-14756, 2023.

17:00–17:10
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EGU23-15331
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ECS
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On-site presentation
Behnam Mirgol, Bastien Dieppois, Jessica Northey, Jonathan Eden, Lionel Jarlan, Yves Tramblay, Gil Mahé, Ikram El Hazdour, Saïd Khabba, Lahoucine Hanich, and Michel Le Page

The agriculture sector is sensitive to changes in weather and climate, notably extreme events. Extreme variations in weather conditions throughout a growing season led to changes in phenological features of vegetation and crops and cause variations in harvest, and, generally, the impact could be large in terms of production amounts and then food security in the region. The last version of the Intergovernmental Panel on Climate Change report (IPCC) highlighted the southern Mediterranean region as a hot spot and one of the most vulnerable regions in the world. While numerous studies have addressed changes in climate extremes throughout the world, very little research has been conducted in the southern Mediterranean region concerning the seasonal concurrence of climate extremes, and their evolutions in recent decades.  Moreover, understanding the impacts of these changes on vegetation phenology is crucial in the region, but this is yet to be studied.

This study evaluates the impact of climate extremes on vegetation phenology in the southern Mediterranean region over the last 40 years. Firstly, the trends of 15 phenological vegetation indicators (e.g., length of the growing season, maximum Normalized Difference Vegetation Index [NDVI] value/time, onset/offset times, green upslope, brown downslope, etc.) are examined using National Oceanic and Atmospheric Administration [NOAA] satellite images and the modified Mann-Kendall trend test. Secondly, we examine how recent trends in vegetation phenology compare with those observed in various heat-related indices (heat wave characteristics), water-related indices (Standard Precipitation Index [SPI], Standard Precipitation Evapotranspiration Index [SPEI], Extreme Precipitation, Wet/Dry spells), and compound indices (Dry-Cold, Dry-Hot, Wet-Cold, Wet-Hot events) calculated using the ERA5-land dataset. Finally, we examine the relative importance of each climate indicator in explaining multi-year changes in vegetation phenology. As such, this study not only identifies the areas with higher risk and vulnerability for vegetation and crops in the last years but also identifies potential predictors for seamless seasonal-to-decadal forecasts of agrometeorological risks across the region.

How to cite: Mirgol, B., Dieppois, B., Northey, J., Eden, J., Jarlan, L., Tramblay, Y., Mahé, G., El Hazdour, I., Khabba, S., Hanich, L., and Le Page, M.: Recent trends in vegetation phenology across the southern Mediterranean region, and potential climatic drivers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15331, https://doi.org/10.5194/egusphere-egu23-15331, 2023.

17:10–17:20
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EGU23-3412
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Virtual presentation
Ana Bastos, Sebastian Sippel, Dorothea Frank, Miguel Mahecha, Sönke Zaehle, Jakob Zscheischler, and Markus Reichstein

Weather extremes have multiple impacts on ecosystems, either through direct influence on plant functioning and health, or indirect and lagged impacts through disturbances such as fires, insects or pest outbreaks. Recent decades have seen an increase in high-impact extreme events, such as large-scale drought-induced mortality, crop failure, mega-fires, and widespread tree mortality events.

Understanding to which degree these events are already signs of human-driven climate change requires establishing a reference of natural climatic and ecological variability and formal attribution frameworks. Attribution of single weather extremes is challenging, but feasible through large ensembles of climate model simulations and by advanced statistical techniques. Attribution of high-impact ecological events is, however, complicated by the fact that impacts are not only driven by climate but also by internal ecological dynamics (mortality, gap dynamics, competition, succession) and human influence on the landscape and ecosystem composition (e.g., through land cover change, management, landscape fragmentation, etc.).

Here, we present a systemic framework that brings together climate risk and disturbance ecology perspectives to analyse the causal links between climate extremes, disturbances, and ecosystem dynamics. We propose an extended attribution approach that considers not only anthropogenic effects via climate change but also anthropogenic influences on ecological factors that modulate impacts. Based on this framework and on dedicated simulations by an Earth System Model, we exemplify how eco-climatic storylines can be used for robust attribution of high-impact events.

 

 

How to cite: Bastos, A., Sippel, S., Frank, D., Mahecha, M., Zaehle, S., Zscheischler, J., and Reichstein, M.: Challenges and ways forward in ecological impact attribution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3412, https://doi.org/10.5194/egusphere-egu23-3412, 2023.

17:20–17:30
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EGU23-2776
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On-site presentation
Marcus Reckermann and the BEAR Human Impacts Author team

Coastal environments, in particular heavily populated semi-enclosed marginal seas and coasts like the Baltic Sea region, are strongly affected by human activities. A multitude of human impacts, including climate change, affects the different compartments of the environment, and these effects interact with each other.

As part of the Baltic Earth Assessment Reports (BEAR), we present an inventory and discussion of different human-induced factors and processes affecting the environment of the Baltic Sea region, and their interrelations. Some are naturally occurring and modified by human activities (i.e. climate change, coastal processes, hypoxia, acidification, submarine groundwater discharges, marine ecosystems, non-indigenous species, land use and land cover), some are completely human-induced (i.e. agriculture, aquaculture, fisheries, river regulations, offshore wind farms, shipping, chemical contamination, dumped warfare agents, marine litter and microplastics, tourism, coastal management), and they are all interrelated to different degrees.

We present a general description and analysis of the state of knowledge on these interrelations. Our main insight is that climate change has an overarching, integrating impact on all of the other factors and can be interpreted as a background effect, which has different implications for the other factors. Impacts on the environment and the human sphere can be roughly allocated to anthropogenic drivers such as food production, energy production, transport, industry and economy.

We conclude that a sound management and regulation of human activities must be implemented in order to use and keep the environments and ecosystems of the Baltic Sea region sustainably in a good shape. This must balance the human needs, which exert tremendous pressures on the systems, as humans are the overwhelming driving force for almost all changes we see. The findings from this inventory of available information and analysis of the different factors and their interactions in the Baltic Sea region can largely be transferred to other comparable marginal and coastal seas in the world.

This work is published as Open Access article in Earth System Dynamics (Earth Syst. Dynam., 13, 1–80, 2022; https://doi.org/10.5194/esd-13-1-2022)

How to cite: Reckermann, M. and the BEAR Human Impacts Author team: Human impacts and their interactions in the Baltic Sea region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2776, https://doi.org/10.5194/egusphere-egu23-2776, 2023.

17:30–17:40
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EGU23-3662
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ECS
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On-site presentation
Zhetao Tan, Karina von Schuckmann, Lijing Cheng, and Sabrina Speich

Changes in health and sustainability of the ocean that provide goods and services for human well-being are closely linked to climate change. However, the ocean is exposed to a range of climatic impact-drivers (CIDs, e.g., temperature increase, sea level rise, oxygen depletion, acidification etc.) from global to local scale concurrently. These multiple CIDs make the ocean environment shifting from the normal condition, posing either positive or detrimental effects to ocean ecosystems. Therefore, detecting and understanding the combined effect of different CIDs (named compound CIDs in this study) is critical to further unravel diverse and adverse impacts on the ocean ecosystems.

In this study, we analyzed compound CIDs from changes in the upper 2000m of the ocean temperature (T), salinity (S), and dissolved oxygen (DO) from 1960 to 2022, as well as surface pH changes from 1985 to 2021 by using several observation-based gridded products.

We used a time of emergence (ToE) approach to investigate the long-term change of  the compound CIDs. First, to quantify the ToE of each CID, we investigated when and where the long-term change (signal) is significantly larger than the background variability (noise). The long-term change is quantified by the 20 years of low-pass filtering of global time series, and the background variability is quantified by the magnitude of annual-interannual variability of the local time series. Additionally, the uncertainty of ToE is defined by using an ensemble approach. With the ToE of individual CID available, we defined the regions where ToE of the compound CIDs can be detected if the change of more than one CID has already emerged. The results we obtained provide a new insight on the 3D changing ocean properties. They differ from previous studies that were limited to a subset of individual CID (e.g., sea level rise, chlorophyll-a, net primary production) or to the ocean surface only (e.g., SST).

The analysis shows that, before 2021, for the upper 2000m, ~15% (±5%) of areas of global ocean has experienced the concurrent emergence of three CIDs (triple emergence), and ~30% (±8%) of global ocean has experienced concurrent emergence of two CIDs (double emergence) mainly in the Atlantic and northern Indian Ocean. Analyses at different depths reveal that ToE is stronger and starts earlier in deep layers (200-1300m) than in the upper ocean (0-200m) where the signal-to-noise ratio is lower (which may due to the strong interplay of the long-term change with natural variability).

As marine ecosystems rely on an environment determined by multiple drivers (T/S/oxygen etc.), the investigation of the compound CIDs provides a more complete description (and quantification) of their long-term exposure to the CIDs (multiple stressors).

How to cite: Tan, Z., von Schuckmann, K., Cheng, L., and Speich, S.: Global emergence of compound climatic impact-drivers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3662, https://doi.org/10.5194/egusphere-egu23-3662, 2023.

17:40–17:50
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EGU23-5385
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On-site presentation
Richard Betts, Regan Mudhar, Dann Mitchell, and Peter Stott

We will present findings from a comprehensive review of the detection and attribution of climate change in the UK, including both recent and past events within the observation record. We will highlight where there are notable gaps, including those that can and cannot be closed with existing data and/or attribution techniques.

This systematic review of detection and attribution literature will feed into a report, with a database of supporting evidence, to inform the Climate Change Committee’s upcoming UK Climate Change Risk Assessment. The first part of the review will cover the detection and attribution of weather and climate changes in the UK, relevant to specific Climate Impact Drivers, while the second will cover societal, infrastructural, economic, and biodiversity impacts associated with these. As part of this, we will identify variables which are key drivers of multiple impacts, and, importantly, where further attribution analysis is needed, especially when the impacts are critical for UK risk.

How to cite: Betts, R., Mudhar, R., Mitchell, D., and Stott, P.: Gaps in Attribution for the Next UK Climate Change Risk Assessment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5385, https://doi.org/10.5194/egusphere-egu23-5385, 2023.

17:50–18:00
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EGU23-3679
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Highlight
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On-site presentation
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Michael Wehner, Kevin Smiley, and Christopher Sampson

The human influence on many classes of extreme weather events has been made very clear by extreme weather event attribution studies. However, this is only the first step to quantify the human influence on the actual impacts from these events. Using Hurricane Harvey as a storyline example, we illustrate the causal chain from increased temperatures to increased precipitation to increased flooding to increased structural damages. Detailed geographical information about the effect of climate change on the flood leads to an attribution statement about damages and is combined with census data revealing profound disparities across socioeconomic groups. We leave the listener with rhetorical questions: Can one quantify environmental injustice? If so, can an end to end attribution statement about climate change induced loss and damages provide a defensible claim for reparations?

How to cite: Wehner, M., Smiley, K., and Sampson, C.: From hot air to environmental injustice: end to end event attribution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3679, https://doi.org/10.5194/egusphere-egu23-3679, 2023.

Posters on site: Wed, 26 Apr, 14:00–15:45 | Hall X5

Chairpersons: Sabine Undorf, Sebastian Sippel, Aurélien Ribes
X5.294
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EGU23-2684
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ECS
Anju K. Vijayan and Pradeep P. Mujumdar

Anthropogenic climate change is one of the most pressing global environmental challenges faced by society in recent times. Large-scale shifts are observed in precipitation and runoff patterns due to the impact of anthropogenic climate change on the regional water cycle. Understanding these impacts is critical for effectively managing and protecting water resources and for mitigating the impacts of climate change. However, the detection of the impact of anthropogenic climate change on the regional water cycle is challenging. A pattern correlation analysis using fingerprints can be carried out to evaluate the impacts of human-induced climate change. Fingerprints give the expected direction of the anthropogenic signal and help to reduce the detection problem to a univariate or low-dimensional problem. This study adopts a formal fingerprint-based detection method to analyze the trends in monsoon precipitation and streamflow in the Krishna River basin, India. In-situ observations and several climate model outputs are utilized for the analyses. Principal component analysis, statistical downscaling techniques, and an Artificial Neural Network (ANN) based rainfall-runoff model are employed. The fingerprint detection method is illustrated using three scenarios by altering the anthropogenic forcings: aerosols alone, land use alone, and a combination of greenhouse gases with aerosols. The hydrologic variables considered are the gridded monthly monsoon precipitation data for 1951-2005 at 1° latitude by 1° longitude and monthly monsoon streamflow at a downstream gauging station. Leading Empirical Orthogonal Functions (EOFs) and signal strength are used to compare the response pattern of observed hydrologic variables with the response pattern simulated by climate models, including various forcings. The hypothesis that the observed trend in hydrologic variables lies within the range expected from natural internal variability alone is validated at a 95% statistical confidence level for most of the climate models considered. This excludes the possibility of other causal factors, including solar irradiance, volcanic eruption, and other anthropogenic impacts. It is found that the signal of human influence is less distinct from that of natural variability. Hence, it is concluded that applying a formal fingerprint-based method is not fully successful in detecting anthropogenic trends in hydrologic variables at the basin scale. The results emphasize the need for robust observational data and advanced analytical techniques considering a detailed process understanding.

How to cite: K. Vijayan, A. and P. Mujumdar, P.: On detecting signals of anthropogenic climate change in basin-scale hydrologic variables, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2684, https://doi.org/10.5194/egusphere-egu23-2684, 2023.

X5.295
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EGU23-3768
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ECS
Kaiwen Zhang, Zhiyan Zuo, Renhe Zhang, Dong Xiao, and Liang Qiao

The signal of temperature change has emerged from background variations in most tropical regions in boreal summer over decadal-centennial timescales but not in northern-central India (NCI). In this study, we investigated the reason for the limited temperature change in NCI. We found that internal variability, largely caused by the Interdecadal Pacific Oscillation (IPO) on a ∼20-year timescale, has the potential to mask the temperature change signal. Besides, local response to external forcing, linked to non-greenhouse gas (GHG) forcings, strongly overrides GHG warming in NCI, which results in little trend in the temporal evolution of external variability. The internal variability related to IPO and the limited warming arising from the competition between multiple forcings result in the smallest signal-to-noise ratio and thus, the temperature change signal fails to emerge from the background variations.

How to cite: Zhang, K., Zuo, Z., Zhang, R., Xiao, D., and Qiao, L.: Constrained Emergence of Air Temperature Change Signal in Northern-Central India From Background Variations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3768, https://doi.org/10.5194/egusphere-egu23-3768, 2023.

X5.296
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EGU23-6020
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ECS
Daniel Cotterill, Dann Mitchell, Peter Stott, and Paul Bates

The risk of flash flooding is likely to increase with the intensification of short-duration rainfall extremes due to Climate Change. Using the latest convective-permitting resolution climate model data for the UK and the LISFLOOD-FP flood inundation model, we adopt a trend detection approach to attribute flash flooding impacts over the UK city, Leeds. Our study is based on an extreme rainfall event in August 2014, where over 400 properties were flooded after 80mm of rainfall fell in five hours in parts of the city. This research will be the first attribution study for UK pluvial flood impacts, using pure convective-permitting resolution climate model data.  The flood inundation model simulates flood maps for over 12 000 events using soil moisture and rainfall data as inputs.

How to cite: Cotterill, D., Mitchell, D., Stott, P., and Bates, P.: The attribution of flash flooding impacts over cities in the United Kingdom, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6020, https://doi.org/10.5194/egusphere-egu23-6020, 2023.

X5.297
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EGU23-7932
Médéric St-Pierre, Mojib Latif, Joakim Kjellsson, Wonsun Park, and Leonard Borchert

During the last few decades, the European climate has changed significantly. Extreme temperatures are now more frequent than ever since the start of industrialization and changes in the water cycle evident. The soil water content could be affected by these changes disturbing the daily life of many people. More often than we would like, anthropogenic factors and more specifically the CO2 emissions are found to be the causes of these perturbations. In this study, we look into the European soil moisture trends in a changing climate. To achieve this, we use a single grand ensemble of 100 members performed with the Kiel Climate Model (KCM). Each simulation starts with different initial conditions taken from a pre-industrial control run and is forced by a 1%-CO2 increase per year. This means that the atmospheric CO2-concentration doubles after 70 years and quadruples after 140 years. Strong drying over most of Europe is simulated with more than 95% of the ensemble members agreeing on the sign of the change. Central Europe experiences a particularly large drying during spring and summer, while the Mediterranean region is affected all year long by drying. The northern European soil moisture also decreases, but to a lesser extent. The changes over all of Europe are mainly due to a reduction in precipitation and, to a certain degree, an increase in evaporation. Precipitation trends in the KCM ensemble are in good agreement with that in the CMIP6 models forced by the shared socioeconomic pathway 5-8.5 (SSP585).

How to cite: St-Pierre, M., Latif, M., Kjellsson, J., Park, W., and Borchert, L.: Evident decrease in future European soil moisture in the Kiel Climate Model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7932, https://doi.org/10.5194/egusphere-egu23-7932, 2023.

X5.298
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EGU23-11209
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ECS
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Highlight
Hye-Yeon Kim, Eun-Ji Song, Min-Ho Kwon, and Baek-Min Kim

The origin of characteristic increase of continental-scale summer surface temperature in decades over Northern hemisphere was investigated. July-temperature in Europe, East Asia, the North Pacific, and western North America have been undergoing more increase than the global average of about 1ºC increase, especially in recent years. On the contrary, MME of 37 CMIP5 models do not show the focused regional warming hot-spots but exhibits hemispheric surface temperature increase. From the comparison between GISTEMP observation record and CMIP5 MME historical data, we show an evidence that the observed characteristic increase of regional temperature for the recent 43 years is dominated by the Internal Climate Variability (ICV) of decadal time-scale. Performing EOF analysis on the ICV, the four dominant modes are identified as Pacific Decadal Oscillation (PDO), North Pacific Oscillation (NPO), Pacific Meridional Mode (PMM), and Atlantic Multi-decadal Oscillation (AMO). It is also shown that, with only two dominant modes among those modes, large portion of continental-scale temperature increase can be explained: We show that PDO and PMM are dominant modes in Europe and East Asia, NPO and AMO in the North Pacific, and PDO and NP in western North America. The observed sub-trend is nicely reproduced with only these two modes. Quantitatively, the observed sub-trend from ICV explains 73%, 60%, 55%, and 18% of the total variability in North Pacific, East Asia, western North America and Europe, respectively. Note that, despite 82% of temperature fluctuation in Europe is attributed by the external forcing, 18% of the internal variability is still important to explain the increasing number of extreme heat events in Europe in recent several decades.

How to cite: Kim, H.-Y., Song, E.-J., Kwon, M.-H., and Kim, B.-M.: Significant Role of Internal Climate Variability for the Global Warming Hot-spots in the Northern Hemisphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11209, https://doi.org/10.5194/egusphere-egu23-11209, 2023.

X5.299
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EGU23-11482
Joanna Wibig and Joanna Jędruszkiewicz

On the basis of data from the period 1966-2020 from about 50 stations in Poland the precipitation and potential evaporation indices will be estimated and their variability analyzed. Different formulas of potential evapotranspiration, based on air temperature, relative humidity, saturation deficit, wind speed and/or sunshine duration, will be compared. Climatic water balance defined as a difference of precipitation and potential evapotranspiration will be calculated and its intraannual variability analyzed. Long-term changes of all three parameters (precipitation, evapotranspiration and climatic water balance) in the context of contemporary warming will be examined. On this basis, the problem of water availability in various regions of the country will be discussed, especially in the context of changes in the spatial distribution and duration of the snow cover. 

How to cite: Wibig, J. and Jędruszkiewicz, J.: Climatic water balance in Poland – intraannual variability and longterm trends, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11482, https://doi.org/10.5194/egusphere-egu23-11482, 2023.

X5.300
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EGU23-14095
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ECS
TaeHun Kang, Donghyuck Yoon, Dong-hyun Cha, and Myong-In Lee

To investigate the recent change of tropical night in South Korea, the duration and intensity of tropical nights (daily minimum temperature , Korea Meteorological Administration; KMA) were quantitatively analyzed for 40 years (1979-2018). As a result of spatiotemporal analysis, There were stronger and longer-lasting tropical nights in the Seoul metropolitan area compared to other regions of South Korea. In particular, the tropical nights over the region tended to increase more prominently in terms of intensity, frequency, and duration.

The tropical night event in the metropolitan area was classified into pure-TN (no heatwave prior to tropical night) and HWTN (tropical night following heatwave). In the analysis of climatological synoptic conditions based on 40-year ERA5 data, two types of tropical night events (pure-TN and HWTN) occurred. Pure-TN occurred when a mid-level anticyclone circulation existed over the Korean Peninsula with the southwesterly which induced a positive temperature advection anomaly over the metropolitan area. Moreover, a positive low cloud cover anomaly with enhanced downward longwave radiation also prevailed. On the other hand, HWTN mainly occurred when a mid-level cyclone circulation was located over the Korean Peninsula with a positive downward shortwave radiation anomaly and a descending motion anomaly that induced adiabatic heating over the metropolitan area.

Significant increasing trends in tropical night events (pure-TN: 0.143 day/year, HWTN: 0.077 day/year) appeared at 95% confidence level. The regression analysis was also conducted for three sub-analysis periods with 10 days (21-31 July;P1, 1-10 August;P2, 11-20 August;P3). Consequently, the favorable atmospheric conditions for HWTN (pure-TN) have been frequently constructed during P2 (P1, and P3).

How to cite: Kang, T., Yoon, D., Cha, D., and Lee, M.-I.: Recent changes of tropical night in the South Korea metropolitan area, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14095, https://doi.org/10.5194/egusphere-egu23-14095, 2023.

X5.301
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EGU23-14441
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ECS
Zhongwei Liu, Jonathan Eden, Bastien Dieppois, Igor Drobyshev, Stefaan Conradie, Carolina Gallo, and Matthew Blackett

In recent years, the occurrence of a series devastating wildfire events around the world has raised considerable public concern about how climate change is altering meteorological conditions conducive to such events. The relative scarcity of wildfire attribution studies, coupled with the limited observational record, has added to the difficulty of developing reliable collective conclusions for future forest management strategies. Recent work has discussed the uncertainties and sensitivities associated with the choice of meteorological indicator to represent fire weather and the validation of climate model ensemble in the context of extreme event attribution, but the value of linking the attribution of recent record-breaking wildfire events with future risk assessment has not yet been fully explored.

Here, using an established probabilistic framework based on extreme value theory, we present the findings of attribution analysis applied to a series of recent high-impact wildfire. In each case, fire weather extremes, represented by annual maxima of the Canadian Fire Weather Index (FWI), are fitted to an extreme value distribution and scaled to the global mean surface temperature. Probability ratios are used to quantify the influence of rising global temperatures on the changing frequency of FWI extremes for past, present and future climates. We demonstrate the value of the application of a common methodological framework in combining results from different case studies as part of a collective attribution approach for multiple extreme across several world’s fire-prone regions. Further analysis of future risks will provide robust recommendations to reduce and address the hazards posed by wildfires and to improve post-disaster resilience.

How to cite: Liu, Z., Eden, J., Dieppois, B., Drobyshev, I., Conradie, S., Gallo, C., and Blackett, M.: Collective attribution and future risk assessment of recent high-impact wildfire events, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14441, https://doi.org/10.5194/egusphere-egu23-14441, 2023.

X5.302
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EGU23-15031
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Veronika Huber, Susanne Breitner-Busch, Alexandra Schneider, and Matthias Mengel

Past studies quantifying the burden of heat-related mortality attributable to climate change have mostly focused on specific extreme events or considered multi-decadal averages. Here, we contribute to the scarce literature on the attribution of observed temporal trends in heat-related mortality to climate change. Our study is based on daily all-cause mortality time-series from 15 major German cities over 1993-2020. Counterfactual climate data is derived from century-long measurement series of daily mean temperatures by removing trends related to the observed rise in global mean temperature according to the ATTRICI method. We use quasi-Poisson regression models including distributed lag non-linear models and multivariate meta-regression models to estimate temperature mortality associations. Our results corroborate previous model-based estimates, suggesting that, averaged over the entire study period, 28% (95%CI: 17%, 42%) of warm-season (May-Sep) heat-related excess mortality across all German cities were attributable to climate change. Considering linear temporal trends suggests that this proportion has increased by 4.0±1.0% per decade. Under observed climate change, we find a linear increase of 174 (SE: ±151) heat-associated deaths per decade across cities. By contrast, our results suggest that without climate change there would not have been a significant increase in heat associated deaths. Overall, our study provides evidence of increasing impacts of climate change on heat-related mortality in Germany since the 1990s. As temperatures keep rising in the future, climate change is expected to drive further increases in heat-related excess mortality unless additional adaptive measures are taken.

How to cite: Huber, V., Breitner-Busch, S., Schneider, A., and Mengel, M.: Attributing observed trends in heat-related excess mortality to climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15031, https://doi.org/10.5194/egusphere-egu23-15031, 2023.

X5.303
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EGU23-15387
Daniele Bocchiola and Lucia Ferrarin

Weather data observed all over the world show an increase in the frequency of extreme events, leading to higher economical losses and numbers of victims. It is thus crucial to investigate causes of such trends, and future evolutions thereby. A method for climate attribution is to assess as to whether anthropogenic climate change affected either the probability of occurrence/or the magnitude of extreme events. Results thereby are fundamental to link extreme event impacts and global warming, and could potentially be used to assess responsible subjects, under the perspective e.g. of setup of compensation policies. Attribution studies so far have shown large uncertainty, especially concerning weather events affected by other drivers than temperature (e.g. precipitation, drought, snow-fall events). As a first step to perform an attribution study one has to identify/quantify a trend of one or more variable(s)/indexes affecting the event under analysis.

Here, we applied statistical methods to identify potential trends, and to back-attribute them to global warming. Using synthetically generated a-priori known, trend-affected series of meteorological variables (P,T, etc..), we (try and) back-trace the presence/magnitude of trends, and try and verify measurable changes of the statistical (extreme values) distribution thereby, for the purpose of robust  climate attribution.  

The goal is to quantify how much results of an attribution study depend upon data type (ground based, climate models, etc..), and accuracy thereby, and upon (robustness of) the trend detection method applied in the analysis.

For an application to a real world case study, we selected variables of interest (precipitation/snowfall extremes) in the Alps of Italy, and we tested the results of the methodology, by assessing trend presence/magnitude of extreme events distributions’ parameters, and robustness thereby.  

How to cite: Bocchiola, D. and Ferrarin, L.: Climate attribution for extreme events. A statistically based approach., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15387, https://doi.org/10.5194/egusphere-egu23-15387, 2023.

X5.304
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EGU23-15912
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ECS
Péter Szabó, Judit Bartholy, and Rita Pongrácz

Although anthropogenic global warming is well-described in the climate community, some socioeconomic groups are still skeptical about it due to various reasons, and they do not know how to associate local weather or climate events with global warming. It is our duty to raise awareness by conveying easily understandable yet scientifically sound and straightforward information and to explain how human activity contributes to climate impacts in front of our eyes, in our region. Although it is widely assessed now in Western Europe, in Hungary from September 2021 we began our comprehensive analyses and raised awareness in several social strata through our local attribution project.

Within the project, we selected seasonally relevant and publicly well-known climate indicators (e.g., vegetation start in spring, heatwaves and forest aridity in summer, second summer in autumn, snow in winter), since they either have a fairly large public interest or have big impacts in our region. Dissemination is done mainly via a well-known online Hungarian platform with broad media coverage, while their social media network is also used with short messages. Results are published in each season at around an event occurrence or absence (e.g., when there is no snow in winter, when vegetation starts too early in spring).

For the analysis, we used several state-of-the-art data sets consisting of global climate model simulations with both natural-only and historical forcings, an ensemble of regional climate model simulations with strong mitigation and non-mitigation future scenarios, and high-quality, gridded observations.

How to cite: Szabó, P., Bartholy, J., and Pongrácz, R.: Attribution of seasonally-relevant climate indicators in Hungary, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15912, https://doi.org/10.5194/egusphere-egu23-15912, 2023.

Posters virtual: Wed, 26 Apr, 14:00–15:45 | vHall CL

Chairpersons: Sabine Undorf, Sebastian Sippel, Aurélien Ribes
vCL.6
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EGU23-8900
George Katavoutas, Dimitra Founda, Konstantinos V. Varotsos, and Christos Giannakopoulos

Many regions across the globe have been witnessing changes in both mean climate and climatic extremes during the last decades. Cities in particular, where the concentration of urban population is high, have been in the spotlight of scientific research seeking to address climate-related issues. At the same time, climate change is expected to largely impacts cities until the end of 21st century. However, changes in air temperature levels, as an essential element of the climate, are probably not uniform nor of the same rate across different areas of the globe. An important indicator of the global climate change is the diurnal temperature range (DTR), defined as the difference between the daily maximum and daily minimum air temperature, thus reflecting the temperature variation within a day.

This study analyses the distribution and long-term trends in DTR in seventeen European cities of different base climate. The response of DTR under exceptionally hot weather has also been investigated. The study uses observed and projected data of daily maximum and minimum air temperature over the periods 1961-2019 and 1971-2100, respectively. The projected data, over the studied cities for the closest land grid point to the stations’ location, were derived from the Regional Climate Model (RCM) RCA4 of the Swedish Meteorological and Hydrological Institute driven by the Max Planck Institute for Meteorology model MPI-ESM-LR, with the simulations carried out in the framework of the EURO-CORDEX modeling experiment. The projected data were bias adjusted applying the empirical quantile mapping technique. Future simulations were based on two climate scenarios, the Representative Concentration Pathways (RCPs) 4.5 and 8.5.

The distribution of the DTR frequency based on observations shows a similar pattern in cities that share the same background climate, while is clearly differentiated at diverse climate types. The mean DTR for normal summer days (maximum air temperature lower than 95 percentile) ranges between 8.0 and 10.5 oC for all cities, with the exception of Nice that shows lower mean DTR and Nicosia, Madrid and Bucharest that present higher. The change of the mean DTR between summer normal days and hot days (maximum air temperature higher than 95 percentile) is greater for cities in higher latitudes, while it is smaller for cities in lower latitudes. According to the projected data for the period from 1971 to 2100 under the RCP4.5 scenario, a statistically significant decreasing trend in mean DTR/yr is projected for the cities in the highest latitudes (Oslo, Stockholm and Helsinki), suggesting higher increasing rates in the minimum air temperature compared to the maximum air temperature. At the same time, the opposite result is expected in Madrid (statistically significant increasing trend), while no statistically significant trends in mean DTR are projected for the rest of the cities.

How to cite: Katavoutas, G., Founda, D., Varotsos, K. V., and Giannakopoulos, C.: Observed and projected changes in the diurnal temperature range at European cities with different base climate, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8900, https://doi.org/10.5194/egusphere-egu23-8900, 2023.