First contributions to the Climate of the 20th Century Detection and Attribution Project

This poster presents results of a pilot effort in preparation for the international WCRP CLIVAR Climate of the 20th Century (C20C) Detection and Attribution Project. The C20C project will produce large ensembles of simulations of the climate we have experienced using multiple atmospheric models driven by observed boundary conditions, as well as large ensembles of simulations for various estimates of the climate that might have been had human activities not interfered with the climate system. These ensembles will allow characterization of how anthropogenic emissions have contributed to the risk of extreme weather events over the past half century, as well as discerning changes in seasonal predictability and in the frequency of extreme events during that period. Here we report on an early contribution using three atmospheric models, examining how anthropogenic greenhouse gas emissions have contributed to the risk of various events during the 2009-2011 period. A near-identical experimental protocol has been followed with all three models, according to the proposed protocol for the C20C project, allowing for a indication of the importance of model selection for assessment of attributable risk, and the degree to which estimates of attributable risk using the time-slice atmospheric modelling approach vary from year to year.