August 15, 2013
The recent decade has seen an exceptional number of extreme heat waves around the world that caused severe damage to society and ecosystems. Examples of such events include the European heat wave of 2003, the Greek heat wave of 2007, the Australian heat wave of 2009, the Russian heat wave of 2010, the Texan heat wave of 2011, and the US heat wave of 2012.
Climatic warming of about 0.5oC in the global mean since the 1970s has strongly increased the occurrence-probability of heat extremes on monthly to seasonal time scales. For the 21st century, climate models predict more substantial warming. Dim Coumou and Alexander Robinson (Potsdam Institute for Climate Impact Research) have shown that the multi-model mean of the CMIP5 (Coupled Model Intercomparison Project) climate models accurately reproduces the evolution over time and spatial patterns of the historically observed increase in monthly heat extremes. For the near-term (i.e., by 2040), the models predict a robust, several-fold increase in the frequency of such heat extremes, irrespective of the emission scenario. However, mitigation can strongly reduce the number of heat extremes by the second half of the 21st century. Unmitigated climate change causes most (>50 %) continental regions to move to a new climatic regime with the coldest summer months by the end of the century substantially hotter than the hottest experienced today. Scientists have shown that the land fraction experiencing extreme heat as a function of global mean temperature follows a simple cumulative distribution function, which depends only on natural variability and the level of spatial heterogeneity in the warming.
http://iopscience.iop.org/1748-9326/8/3/034018?fromSearchPage=true