Climate Extremes: Changes, Impacts, and Projections

This workshop brought together modelers, climate monitoring diagnosticians, social scientists, and ecologists to discuss societal and ecological impacts of weather and climate extremes and cascading impacts. In addition to integrating available information from diverse fields, this workshop also discussed opportunities for reducing uncertainty in projecting and planning for extreme events.

Keywords: models and modeling; human impacts; ecology; climate variability and change; weather, extremes

Overview & Relevance:
There is general agreement that changes in the frequency or intensity of extreme weather and climate are likely to have profound impacts, both ecologically and on human society. These changes may be long-term trends or decadal fluctuations, and distinguishing be- tween the two is a major issue which we can only address with the use of both model simulations and analysis of the past climate record. Understanding the linkages among climate and weather extremes and their impact on societies, infrastructure, and on managed and natural ecosystems, are areas of major uncertainty. This is highlighted by sectoral and regional differences in responses to the impacts of weather and climate extremes. Teasing out these relationships between the physical climate system and its impacts is a major focus of the U. S. National Climate Change Assessment that is underway.

Content:
The Aspen Global Change Institute summer meeting on Climate Extremes brought together modelers, climate monitoring diagnosticians, and climate impact experts (social scientists and ecologists) to better understand this interdisciplinary issue. A number of questions were posed and discussion focused around these issues:

Climate Models
What do climate model simulations tell us about past and projected changes in climate and weather extremes, given past and projected changes in radiative forcing?

Observations
What does the observational record indicate about changes in weather and climate extremes?

Climate Impacts
What do we know about the sensitivity of various systems (both human and ecological) and the dependence among systems related to the frequency and intensity of weather and climate extremes?

For all areas
What are the major uncertainties and the highest research and monitoring priorities? What are the impediments to linkages among these three areas of research, and how might they be resolved?

Understanding the linkages among climate and weather extremes and their impact on societies’ infrastructure, and on managed and natural ecosystems, are areas of major uncertainty. As was anticipated by the meetings” Chairs, the AGCI groups’ collective insights have been summarized in a set of review articles which have been published in The Bulletin of the American Meteorological Society (BAMS).