CL3.1.10

With progressing global warming, there is an increased risk that one or several climate tipping elements might cross a critical threshold, resulting in severe consequences for the global climate, ecosystems and human societies. Here, we study a subset of four tipping elements and their interactions in a conceptual and easily extendable framework: the Greenland Ice Sheet, the West Antarctic Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC) and the Amazon rainforest.

In a large-scale Monte-Carlo simulation, we explicitly investigate the domino effects triggered by each of the individual tipping elements under global warming in equilibrium experiments. Thereby, we reveal the roles of each of the individual tipping elements in cascading transitions. Further, we perform a comprehensive basin stability analysis to detect the stable states of the interacting system and discuss their associated Earth system resilience. Finally, we analyse whether additional internal temperature feedbacks of the tipping elements might be able to increase the risk of triggering tipping events and cascades.

In our model experiments, we find: (i) the Greenland and the West Antarctic Ice Sheet are often the initiators of tipping cascades, while the AMOC typically takes on the role as a mediator of cascades. (ii) The interactions between the tipping elements considered here overall have a destabilizing effect on the climate system as a whole. (iii) In our model, the large ice sheets are of particular importance for the resilience of the Earth system on long time scales, as found by basin stability measures. (iv) Additional internal temperature feedbacks of the tipping elements can slightly increase the risk of triggering tipping events.

How to cite: Wunderling, N., Donges, J., Kurths, J., Gelbrecht, M., and Winkelmann, R.: Interactions of climate tipping elements and their associated basin stability in a conceptual model for tipping cascades, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2941, https://doi.org/10.5194/egusphere-egu21-2941, 2021.

Green water - soil moisture, evaporation, and precipitation over land - is fundamental to safeguard Earth system functioning. Nonlinear green-water driven changes in climate, ecosystems, biogeochemistry, and hydrology are becoming increasingly evident and widespread. Yet, considerations of continental to planetary scale green-water dynamics are yet to be assessed and incorporated in management and governance. Here, we propose a green water planetary boundary (PB) - as part of the planetary boundary framework that demarcates a global “safe-operating space” for humanity - for assessing green-water related changes that can affect the capacity of the Earth system to remain in Holocene-like conditions. We consider green-water related processes associated with all scales: spatially distributed units, regions or biomes, and the Earth system as a whole. The proposed green water PB variable is selected through expert elicitation based on a set of transparent evaluation criteria that consider both scientific and governability aspects. Finally, we clarify the appropriate use of a green water PB, outline remaining challenges, and propose a research agenda for future navigation and quantitative assessments of the biophysical Earth system scale boundaries of green water changes.

How to cite: Wang-Erlandsson, L., van der Ent, R., Staal, A., Porkka, M., Tobian, A., te Wierik, S., Fetzer, I., Singh, C., Jaramillo, F., Greve, P., Gerten, D., Keys, P., Dahlmann, H., Gleeson, T., Steffen, W., Cornell, S., and Rockström, J.: Towards a green water planetary boundary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13583, https://doi.org/10.5194/egusphere-egu21-13583, 2021.

UNESCO Biosphere Reserves are model regions for sustainable development per definitionem. Its management is oriented towards meeting the SDGs and to develop practical and innovative solutions on the ground and study interlinkages between global development and local impacts.

Monitoring is thus an essential tool for the effective management of a biosphere reserve. However, resources and capacities at local level are often limited. The authors outline the major conceptual challenges in developing a long-term monitoring system. In the Salzburger Lungau & Carinthian Nockberge UNESCO BR, a BRIM was elaborated between 2011 and 2013 to map the development and performance of the BR based on only 12 indicators. This system allows for collecting data at BR-level to increase the local ability to detect and link long-term social, economic and ecological changes in an easy-to-apply manner. These datasets can provide a valuable contribution to interpret local impacts of global changes and the related impacts of management actions.

The presenters reflect on the practical experiences and outline as well as a way forward towards future options for viable monitoring systems. The presenters assume that the future of biodiversity monitoring will lie in autonomous or semi-autonomous systems. In this context, disruptive technologies (for example, high-resolution remote sensing, bio-acoustics or genetic techniques such as e-DNA , etc.) will play a central role.

Authors:

Michael Jungmeier* und Michael Huber**

* UNESCO Chair for Sustainable Management of Conservation Areas, Carinthia University of Applied Sciences

** E.C.O. Institute of Ecology, Lakeside B07b, 9020 Klagenfurt, Austria

How to cite: Jungmeier, M. and Huber, M.: A low-cost BRIM (Biosphere reserve integrated monitoring)? The example of the Salzburger Lungau & Kärntner Nockberge BR (Austria), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4730, https://doi.org/10.5194/egusphere-egu21-4730, 2021.

The call for this session mentions that “Earth system resilience critically depends on the nonlinear interplay of positive and negative feedbacks of biophysical and increasingly also socio-economic processes. These include dynamics in [many physical events], as well as the dynamics and perturbations associated with human activities.“ In this contribution, I would like to mobilize a few notions to discuss this issue.

A typical approach is to scale up human dimensions to Earth system model scales. Humans become aggregated into social structures, even societies, that change every year or so. I propose to scale down the Earth system to humans, both in terms of space and time. I think this offers exiting possibilities to study climate and earth systems in a different way, but also allows for answering the question how we could act today, tomorrow and next week in order to understand which long-term scenarios over decades are more likely to occur.

This would move us away from the view of the Earth as a single system or pattern to a perspective of Earth as an interconnected world of different non-human and human agencies. I would position this idea against the rather popular metaphor of the butterfly effect, “the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state”. This may be too simple, as one butterfly will meet many other butterflies along the way. As such, the butterfly effect may be a specific example that claims a certain agency for smaller actors within the Earth System, but that builds its analysis on pattern replication through non-linear relations.

Our (perceived) knowledge of patterns colors our analysis of those patterns. We are all familiar with the metaphor of the men observing different parts of the elephant. The metaphor assumes that we know that what the men are examining is an elephant. However, once we do not know either what they are looking at, we need to start with them seeing different things. In the perspective that we know the elephant, the men are just short-sighted. In the more realistic setting that we cannot be certain about what the men observe, we are the ones that need to come up with a convincing way to analyze what is happening, has happened or may happen.

Much work in Earth system modelling model patterns in society, but do not explain how these patterns are the result of continuously performing agencies. The models are built to mimic the patterns that we observed. I propose to replace the patterns we use to explain the same patterns – whether they are power relations or gravity – with representations of the interacting agencies that together produce the Earth system that we think we observe. Gravity may be a nice explanation of the observed pattern that we do not glide away from the surface, but it remains just that. In our modelling efforts, we may apply the notion that gravity acts.

How to cite: Ertsen, M.: Butterflies, Elephants and Gravity to Model Human-Earth Interactions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9962, https://doi.org/10.5194/egusphere-egu21-9962, 2021.

The Greenland Ice Sheet (GIS) and the Atlantic Meridional Overturning Circulation (AMOC) have been identified as possible tipping elements of the climate system, transitioning into a qualitatively different state with the crossing of a critical driver threshold. They interact via freshwater fluxes into the North Atlantic originating from a melting GIS on the one hand, and via a relative cooling around Greenland with a slowdown of the AMOC on the other. This positive-negative feedback loop raises the question how these effects will influence the overall stability of the coupled system. Here, we qualitatively explore the dynamics and in particular the emergence of cascading tipping behavior of the interacting GIS and AMOC by using process-based but still conceptual models of the individual tipping elements with a simple coupling under idealized forcing scenarios.

We identify patterns of multiple tipping such as (i) overshoot cascades, developing with a temporary threshold overshoot, and (ii) rate-induced cascades, arising under very rapid changes of tipping element drivers. Their occurrence within distinct corridors of dangerous tipping pathways is affected by the melting patterns of the GIS and thus eventually by the imposed external forcing and its time scales.

The conceptual nature of the proposed model does not allow for quantitative statements or projections on the emergence of tipping cascades in the climate system. Rather, our results stress that it is not only necessary to stay below a certain critical threshold to hinder tipping cascades but also to respect safe rates of environmental change to mitigate domino effects and in turn to maintain the resilience of the Earth system.

How to cite: Klose, A. K., Donges, J. F., Feudel, U., and Winkelmann, R.: Cascading tipping behavior of the interacting Greenland Ice Sheet and Atlantic Meridional Overturning Circulation in a model of low complexity, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8436, https://doi.org/10.5194/egusphere-egu21-8436, 2021.

Can the 1.5 deg C warming target still be met with an aggressive phaseout of fossil fuels coupled with a 100% replacement by renewable energy?  We address this question in our modeling study by computing the continuous generation of global wind/solar energy power along with the cumulative carbon dioxide equivalent emissions in a complete phaseout of fossil fuels over a 20 year period. We assume a baseline of energy status at 2018, as well as the EROI of currently available wind/solar energy technologies.  We compare these computed emissions with the state-of-the-science estimates for the remaining carbon budget of carbon dioxide emissions consistent with the 1.5 deg C warming target. Our conclusion is that it is still possible to meet this warming target if the creation of a global 100% renewable energy transition of sufficient capacity begins very soon, coupled with aggressive negative carbon emissions. The latter technology uses a fraction of total renewable energy delivery for direct air capture for permanent crustal storage over the last ten years of this energy transition that is compatible for simulations with no more than 10 to 15 % reinvestment of renewable energy to make more of itself. More efficient renewable technologies in the near future will make this transition easier.  The maximum amount of fossil fuel consumed in our scenarios for the complete transition is no more than 5% of the proven reserves of coal, natural gas and oil as currently estimated.  

How to cite: Schwartzman, D. and Schwartzman, P.: Can the 1.5 deg C warming target be met in a global transition to 100% renewable energy?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10444, https://doi.org/10.5194/egusphere-egu21-10444, 2021.

Mountain glaciers have a delayed response to climate change and are expected to continue to melt long after greenhouse gas emissions have stopped, with consequences both for sea-level rise and water resources. In this contribution, we use the Open Global Glacier Model (OGGM) to compute global glacier volume and runoff changes until the year 2300 under a suite of stylized greenhouse gas emission characterized by (i) the year at which anthropogenic emissions culminate, (ii) their reduction rates after peak emissions and (iii) whether they lead to a long-term global temperature stabilization or decline. We show that even under scenarios that achieve the Paris Agreement goal of holding global-mean temperature below 2 °C, glacier contribution to sea-level rise will continue well beyond 2100. Because of this delayed response, the year of peak emissions (i.e. the timing of mitigation action) has a stronger influence on mit-term global glacier change than other emission scenario characteristics, while long-term change is dependent on all factors. We also discuss the impact of early climate mitigation on regional glacier change and the consequences for glacier runoff, both short-term (where some basins are expected to experience an increase of glacier runoff) and long-term (where all regions are expecting a net-zero or even negative glacier contribution to total runoff), underlining the importance of mountain glaciers for regional water availability at all timescales.

How to cite: Maussion, F., Lejeune, Q., Marzeion, B., Mengel, M., Rounce, D., Schleussner, C., and Schuster, L.: Long-term legacy of delayed climate mitigation in global glacier response, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12898, https://doi.org/10.5194/egusphere-egu21-12898, 2021.

The concept of `resilience' is increasingly being applied in the study of social-technical-environmental systems in Earth system and sustainability science. However, the diversity of resilience concepts and a certain (sometimes intended) openness of proposed definitions can lead to misunderstandings and impede their application to systems modelling. We propose an approach that aims to ease communication as well as to support systematic development of research questions and models in the context of resilience. It can be applied independently of the modelling framework or underlying theory of choice. At the heart of this guideline is a checklist consisting of four questions to be answered: (i) Resilience of what? (ii) Resilience regarding what? (iii) Resilience against what? (iv) Resilience how? We refer to the answers to these resilience questions as the "system", the "sustainant", the "adverse influence", and the "response options". The term `sustainant' is a neologism describing the feature of the system (state, structure, function, pathway etc.) that should be maintained (or restored quickly enough) in order to call the system resilient.
The use of this proposed guideline is demonstrated for two application examples: fisheries, and the Amazon rainforest. The examples illustrate the diversity of possible answers to the checklist's questions as well as their benefits in structuring the modelling process. The guideline supports the modeller in communicating precisely what is actually meant by `resilience' in a specific context. This combination of freedom and precision could help to advance the resilience discourse by building a bridge between those demanding unambiguous definitions and those stressing the benefits of generality and flexibility of the resilience concept. 

How to cite: Tamberg, L., Heitzig, J., and Donges, J.: A modeler's guide to studying the resilience of social-technical-environmental systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11014, https://doi.org/10.5194/egusphere-egu21-11014, 2021.

Tropical rainforests are recognized as one of the terrestrial tipping elements which could have profound impacts on the global climate, once their vegetation has transitioned into savanna or grassland states. While several studies investigated the savannization of, e.g., the Amazon rainforest, few studies considered the influence of fire. Fire is expected to potentially shift the savanna-forest boundary and hence impact the dynamical equilibrium between these two possible vegetation states under changing climate. To investigate the climate-induced hysteresis in pan-tropical forests and the impact of fire under future climate conditions, we coupled the well established and comprehensively validated Dynamic Global Vegetation Model LPJmL5.0-FMS to the coupled climate model CM2Mc, which is based on the atmosphere model AM2 and the ocean model MOM5 (CM2Mc-LPJmL v1.0). In CM2Mc, we replaced the simple land surface model LaD with LPJmL and fully coupled the water and energy cycles. Exchanging LaD by LPJmL, and therefore switching from a static and prescribed vegetation to a dynamic vegetation, allows us to model important biosphere processes, including wildfire, tree mortality, permafrost, hydrological cycling, and the impacts of managed land (crop growth and irrigation).

With CM2Mc-LPJmL we conducted simulation experiments where atmospheric CO2 concentrations increased from a pre-industrial level up to 1280 ppm (impact phase) followed by a recovery phase where CO2 concentrations reach pre-industrial levels again. This experiment is performed with and without allowing for wildfires. We find a hysteresis of the biomass and vegetation cover in tropical forest systems, with a strong regional heterogeneity. After biomass loss along increasing atmospheric CO2 concentrations and accompanied mean surface temperature increase of about 4°C (impact phase), the system does not recover completely into its original state on its return path, even though atmospheric CO2 concentrations return to their original state. While not detecting large-scale tipping points, our results show a climate-induced hysteresis in tropical forest and lagged responses in forest recovery after the climate has returned to its original state. Wildfires slightly widen the climate-induced hysteresis in tropical forests and lead to a lagged response in forest recovery by ca. 30 years.

How to cite: Drüke, M., v. Bloh, W., Sakschewski, B., Wunderling, N., Petri, S., Cardoso, M., Barbosa, H., and Thonicke, K.: Climate-induced hysteresis of the tropical forest in the fire-enabled Earth system model CM2Mc-LPJmL , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8908, https://doi.org/10.5194/egusphere-egu21-8908, 2021.

The concept of planetary boundaries (PBs) was developed to set biophysical limits to human perturbations and to maintain the Earth System at its current steady-state. Research has focused on further updating and improving the PBs, while utilizing them as the conditional basis for sustainable development. A limitation of the current approaches, and focus of our work, is that the PBs closely related to food production are assessed individually without considering their interactions and feedbacks. These PBs include surface water use, land-system change, biogeochemical flows, and biosphere integrity. Such an omission could potentially overestimate the margin for food production within PBs on a local scale, which could have negative implications for sustainable food supply.  

Here, we aim to quantify these interactions with the ultimate goal of estimating a more realistic safe operating space (SOS) for future food production. We build on earlier literature review-based work that identified and quantified many PBs interactions on global scale but was unable to identify and quantify some of the interactions that are important to food production. Thus, we move a step forward by using expert knowledge elicitation to quantify the PBs interactions important to food production at local scale and to qualitatively map the mediating biophysical mechanisms. Expert knowledge elicitation suits the study well since it can fill knowledge gaps when quantitative data is scarce. In this work, we identified the missing links and expanded our knowledge on existing PBs interactions. Following recent work on updating PBs definitions, we divided the biosphere integrity PB into land, freshwater, and ocean components and the surface water PB into blue and green water components. These divisions accommodate for the differences among the Earth System functions. Where needed, we developed new interim control variables to enable quantifying the interaction strengths.

The expert knowledge elicitation was conducted remotely following the IDEA elicitation protocol and utilizing a custom-made web application. A total of 37 experts, in various fields of Earth sciences, completed the process and we received input for all 42 interactions, ranging from 5 to 19 responses each, with a median response rate of 9. We collected both quantitative and qualitative data on interaction strengths, tipping points, and mediating mechanisms, which are aggregated and used in synergy to better describe complex Earth System processes. In addition, we aim to highlight the most important interactions in an effort to prioritize them based on their role in the Earth System and existing knowledge gaps.

How to cite: Chrysafi, A., Jalava, M., Virkki, V., Porkka, M., Sandström, V., Piipponen, J., LaMere, K., Lade, S., and Kummu, M.: Quantifying Planetary Boundaries interaction strengths with expert knowledge elicitation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14639, https://doi.org/10.5194/egusphere-egu21-14639, 2021.

In the Anthropocene, socio-economic systems are an integral and highly interconnected part of Earth System. The internal dynamics of these systems will decide whether the Earth can remain in, or return to, a resilient state that resembles the Holocene. Understanding these dynamics thus represents an important aspect of Earth System Science.

To prevent the irreversible crossing of Planetary Boundaries, a rapid, global societal shift towards decarbonization and sustainability is imperative. Incremental political measures have thus far proven to be insufficient to adequately address this necessity. Social Contagion and Tipping Processes related to sustainable behavior and innovations represent some of the few promising mechanisms by which the societal and economic transformation may be achieved in the remaining window of opportunity.

Such contagion processes are not limited to individual human beings; in their high political responsiveness and cultural radiance, cities may also be viewed as promising agents in the sustainability transformation. Responsible for a dis-proportionally large part of greenhouse gas emissions, and simultaneously one of the main drivers of sustainable policy innovation and implementation, cities may play a unique role in the global sustainability transformation. Learning from each other to reduce, prepare for and react to the coming environmental changes, they can be conceptualized as nodes in a globe-spanning network. Investigating such a learning network model may yield insights into the social tipping dynamics that are so urgently needed to control the human impacts on the Earth System.

The study presented here aims to identify whether network-based contagion effects are dominant in sustainability policy adoption by cities. An attempt is made to approximate the inter-city innovation spreading network using the global air traffic network, political and trade relations, and other city-to-city connections. These networks are extracted from empirical data, and their prediction power is compared. We analyze the spreading of several municipal policies and innovations related to sustainability transformations as contagion processes on these inter-city networks. Surrogate data methods and a dose-response-contagion approach are used to identify network-spreading-correlations. We then investigate the nature of the spreading process by attempting to reproduce it using statistical models. Examples for investigated spreading innovations are the implementation of Bus Rapid Transit public transport systems, and membership in a sustainability organization.

How to cite: Kitzmann, N. H., Donges, J. F., Bai, X., Lade, S., Romanczuk, P., and Winkelmann, R.: Contagious Transformations? Inter-City Spreading of Sustainability Innovations., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8976, https://doi.org/10.5194/egusphere-egu21-8976, 2021.

Weather modification by means of cloud seeding techniques is widely implemented across the world. In areas where hail suppression systems are installed, silver iodide (AgI) particles are used.

Silver particles fall back to the surface thank to atmospheric deposition. In this research we follow a holistic approach to analyse silver accumulation in water, soils and sediments of Aragón (North-East Spain), where AgI emissions have been released for the last fifty years. We have also assessed silver bioaccumulation in plants and biota, and we have tested its effects in plant growth.

Our results show that silver concentrations in water and soils of areas covered by hail suppression networks are higher than in further areas, although concentrations are below legal thresholds. We have also observed that silver seems to be absorbed by plants and biota, which would act as a silver outflow and it may help to remove silver from the ecosystems.

Acknowledgements

This work was funded by Spanish State Research Agency and FEDER Funds via AgroSOS project (PID2019-108057RB-I00) and DONAIRE project (CGL2015-68993-R), and thanks to a pre-doctoral grant awarded by the Government of Aragon to J. M. Orellana-Macías (BOA 20/ 07/2017).

How to cite: Orellana-Macías, J. M., Causapé, J., Pey, J., Valero-Garcés, B., Reyes, J., and Vázquez, I.: Environmental effects of silver iodide emitted by hail suppression systems in Aragón (Spain), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15388, https://doi.org/10.5194/egusphere-egu21-15388, 2021.