How to project climate extremes that really matter? A transdisciplinary approach for new narratives of climate extreme impacts in the future earth context

Session lead: Dr. Jakob Zscheischler (ETH Zürich), Dr. Carl-Friedrich Schleussner (Climate Analytics)

A change in frequency and magnitude of climate extremes in many world regions is one of the inevitable impacts of climate change. Climate related natural disasters have devastating impacts on natural systems and human societies already today. As a consequence, measures of adaptation and disaster risk reduction are crucial to reduce vulnerability and exposure of human and natural systems to climate extremes. These measures have to rely on state-of-the-art projections that provide the basis for science-based decision making and, for the countries of the global south, are a prerequisite to a full access of global climate finance support mechanisms.

Projections of climate extremes and respective risk assessments are usually undertaken by downscaling global climate simulations and translating them into quantities of interest. However, this approach does not allow for feedbacks to the global models nor does it assure full consistency at the local scale. Moreover, in global and regional models extreme events are often not the focus of attention and might not be simulated in the best possible way. Impacts of climate extremes also often depend on weather conditions preceding the extreme, or are magnified by compound extremes. General index-based metrics might fall short of assessing the real risk posed by climate related natural disasters.

Climate projections are usually disconnected from assessments of vulnerability and exposure and thus not sufficient for valuable projections of future disaster risks. Given the highly local case-specific nature of impacts from climate extremes (e.g., forests destruction by storms, coral bleaching through extreme ocean temperatures, salt water intrusion in low lying agricultural fields through floods), top-down approaches might not be the most appropriate tool to capture such interrelations.

A complementary approach could be the integration of stakeholders and adaptation practitioners into the scientific risk assessment and to develop narratives of “future weather” that provide a solid basis for adaptation actions at the ground. Tales of future weather (1) were recently suggested as an alternative to the traditional way of assessing future climate change impacts. Scenarios tailored to a specific region in combination with numerical weather prediction models might offer a more realistic picture of what future weather might look like. In the Tales approach, storylines are developed in a transdisciplinary fashion, including numerical weather prediction experts, local stakeholders and policy makers.

In order to provide the relevant information for building realistic regional scenarios, vulnerabilities of ecosystem services and human systems towards climate extremes have to be assessed first. Data about past climate extremes and their impacts is required to inform future scenarios. Climate data is needed as input to sophisticated weather generators which are able to simulate extremes in a realistic way. A close collaboration between scientists of different disciplines and regional stakeholders is essential to ensure that the focus lies on the most relevant extremes.

While the requirements for such an approach (data availability, local expertise, regional models) are well available and accessible in many industrialized countries (for example adaptation to sea level related extremes in the Netherlands), the probably largest adverse effects of changes in climate extremes will occur in less developed countries (i.e. South-East Asia, Sub-Saharan Africa, and the Small Island States besides others), requiring the highest adaptation efforts. Given the substantial uncertainties in climate projections and vulnerabilities as well as limited capabilities for science-based policy implementation, it is those regions that can benefit most from alternative, narrative-based approaches to assess future weather and risks posed by climatic extreme events. In addition, reasonably precise predictions of potential extreme event impacts at the local level are also a prerequisite to insure future losses.

This workshop brings together scientific experts in climate extremes, vulnerability and resilience science, regional climate and impact modeling, and ecological impacts of climate change as well as stakeholders from regions which are particularly vulnerable to climate extreme impacts including South East Asia, Africa and the Caribbean Islands. In such a transdisciplinary design, frameworks for assessing potential impacts of future climate extremes will be discussed. One of the key topics will be the question of how to develop alternative strategies of predicting future climate extreme impacts when data are scarce and no good regional models are available. The goal of the workshop is to define future research topics that ensure both high scientific quality as well as stakeholder relevance.

(1) Hazeleger, W., B.J.J.M. Van den Hurk, E. Min, G.J. Van Oldenborgh, A.C. Petersen, D.A. Stainforth, E. Vasileiadou, & L.A. Smith (2015). Tales of future weather. Nature Climate Change, 5(2), 107-113