Number of extreme heat days over land continuing to increase

February 26th, 2014 by Nature Climate Change

There has been a continued increase in the number of extreme heat days over land since 1997.

This finding, reported in a Commentary in the March 2014 issue of Nature Climate Change, suggests that the increase is in spite of the recent slowdown in global average surface temperature.

A team of researchers, led by Professor Sonia Seneviratne, analysed observational data to investigate the occurrence of extreme extremes — that is, the number of days hotter than the 90th percentile of a given base period — since 1997.

They looked at the ratio of land area that experiences over 30 days of extreme heat per year compared with the 1979 to 2010 average and found a positive and increasing trend for the period 1997 to 2012.

Additionally, the team examined trends related to different numbers of extreme heat days — for example, 10 extreme heat days versus 50 extreme heat days per year.

They show that the increasing trend in the ratio of land that experiences over 50 extreme heat days is much greater than the increase related to both 30 and 10 days of extreme heat.

Based on these findings, the researchers highlight that it is wrong to interpret the recent slowdown in warming as a general slowdown in climate change.

An increase in extreme heat events, as demonstrated here, is more relevant for impacts and adaptation than global average temperatures.

This article is part of a special Focus in Nature Climate Change entitled ‘Recent slowdown in global warming’, which will be available in the March print issue and online from 26 February 2014.


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