Towards impact-relevant climate extremes metrics

Session lead: Dr. Jana Sillmann (CICERO), Sebastian Sippel (MPI-BGC)

Extreme weather and climate events can have profound impacts on socio-economic systems1. In recent years, such impacts have been widely experienced due to major droughts, heat waves, storms and floods in many regions of the world2, 3, 4. However, the impacts of these extreme events vary depending on their spatio-temporal characteristics and the specific type of event, and are mediated through vulnerability and exposure of the affected socio-economic system. Accordingly, identification and quantification of factors that determine the occurrence and strength of impacts related to weather and climate extremes constitutes a major research challenge.

In the climate science community, “extremes indices” have found widespread application to illustrate and quantify trends in the occurrence of weather and climate extremes on regional to global scales5, 6. However, their definition is commonly based on a univariate and purely climatological framework, which hinders application in a more impact-oriented setting, especially when different types of impacts need to be considered. There is a need to develop new indices, which express an improved understanding of impacts, potentially building on or complementing the currently available climate extremes indices, such as those developed by the Expert Team on Climate Change Detection and Indices (ETCCDI), to increase their relevance to stakeholders. Novel and interdisciplinary approaches are required, which involve a dialogue between scientists and stakeholders and include efforts to share data and knowledge in order to derive socio-economically meaningful “extreme climate” indicators.

The proposed workshop session will bring together stakeholders and scientists from various backgrounds to foster the type of dialogue needed. Novel and exciting questions and topics for future research that improves our understanding about the link between weather and climate extremes and societal impacts will be discussed with the experts from relevant fields.

The outcome of this session will be a summary document, which is intended to initiate a research agenda that will benefit societal adaptation in the face of a changing climate. The overall goal of the anticipated research agenda is to derive suitable metrics that quantify and improve our understanding of the link between weather and climate extremes and societal impacts. While this endeavor is of high societal relevance, it is at the same time scientifically challenging and part of the World Climate Research Programme Grand Challenges on Climate Extremes.
The expert discussions in the session will focus on the following main topics:

i) Providing an overview of different concepts of impact-relevant climate extreme metrics that are used in various fields (heuristic, expert-based, data-driven).

ii) Discussing the feasibility of deriving robust and impact-relevant climate extremes indices - and the potential of adoption and usefulness of such indices for the stakeholder community. These discussions will consider combined (multivariate) extreme indices and the relevance of different spatial and temporal scales.

Further points for discussion will be:

iii) The scope for an inventory of available socio-economic impact data that is crucially important to quantify the extremes – impact link and data-driven indices. The goal here is to derive a continuum of data from biophysical to economic/socio-geographic, including vulnerability and exposure of assets.

iv) The potential to tap novel data streams such as social media.

1. IPCC. Managing the Risks of Extreme Events and Disasters to advance Climate Change Adaptation. Cambridge University Press: Cambridge, UK, and New York, NY, USA, 2012.
2. Herring SC, Hoerling MP, Peterson TC, Stott PA. Explaining extreme events of 2013 from a climate perspective. Bulletin of the American Meteorological Society 2014, 95(9): S1-S104.
3. Peterson TC, Alexander LV, Allen MR, Anel JA, Barriopedro D, Black MT, et al. Explaining extreme events of 2012 from a climate perspective. Bulletin of the American Meteorological Society 2013, 94(9): S1-S74.
4. Peterson TC, Stott PA, Herring S. Explaining extreme events of 2011 from a climate perspective. Bulletin of the American Meteorological Society 2012, 93(7): 1041-1067.
5. Sillmann J, Kharin VV, Zhang X, Zwiers FW, Bronaugh D. Climate extremes indices in the CMIP5 multimodel ensemble: Part 1. Model evaluation in the present climate. J Geophys Res-Atmos 2013, 118(4): 1716-1733.
6. Sillmann J, Kharin VV, Zwiers FW, Zhang X, Bronaugh D. Climate extremes indices in the CMIP5 multimodel ensemble: Part 2. Future climate projections. J Geophys Res-Atmos 2013, 118(6): 2473-2493.