Historic & Future Increase in Global Land Area Affected by Monthly Heat Extremes

Dim Coumou and Alexander Robinson from the Potsdam Institute for Climate Impact Research have published a paper in Environmental Research Letters (open access, free to download) examining the frequency of extreme heat events in a warming world. 

They compared a future in which humans continue to rely heavily on fossil fuels (IPCC scenario RCP8.5) to one in which we transition away from fossil fuels and rapidly reduce greenhouse gas emissions (RCP2.6).  In both cases, the global land area experiencing extreme summer heat will quadruple by 2040 due to the global warming that's already locked in from the greenhouse gases we've emitted thus far.  However, in the low emissions scenario, extreme heat frequency stabilizes after 2040 (left frames in Figure), while it becomes the new norm for most of the world in a high emissions scenario (right frames in Figure).

Historic and Future Increase in the Global Land Area Affected by Monthly Heat Extremes