Challenges in Estimating and Understanding Recent Changes in the Frequency and Intensity of Extreme Climate and Weather Events
World Meteorological Organization (WMO); Alexander, L.V.; Hegerl, Gabriele C.; Knutson, T.R.; Naveau, P.; Nicholls, N.; Schar, C.; Seneviratne, S.I.; Zhang, X.; WCRP OSC Climate Research in Service to Society (24-28 October 2011)
This paper briefly reviews some aspects of the current status of research on changes in climate extremes, identifying gaps and issues that warrant additional work. This paper focuses primarily on the historical instrumental record, giving a sense of the nature of the results that have been obtained, challenges that arise from observational, methodological and climate modelling uncertainties and discussing the extent to which detection and attribution research has been able to link observed changes to external forcing of the climate system. It also very briefly discusses projections for the 21st century. Extremes are not discussed on paleo time scales, in the context of the present (i.e., short term forecasting), or in the context of climate surprises (extreme tipping points). These choices reflect our desire not to attempt too broad a review of the topic due to space constraints of this short paper, as well as a view that very high priority should be given to reducing uncertainty in our understanding of historical changes in extremes over the instrumental period as a prerequisite to confidently predicting changes over the next century. This includes the development of improved and comprehensive observational records, improvement in our ability to confidently detect changes in observations through the development of better physical models, forcing data sets and more power statistical techniques, the development and refinement of our understanding of the physical processes that produce extremes, and continued improvement in our ability to attribute causes to those changes. This does not imply that research on extremes on paleo timescales or on the projection of future changes in extremes is of lesser importance, but rather that overall progress on understanding implications of ongoing and future changes in extremes will be strongly dependent upon our ability to document and understand changes in extremes during the period of history that has been (and continues to be) most comprehensively and directly observed.
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