Time series of temperature anomalies for hot extremes over land (red) and global mean temperature (black, blue). Observational data show a continued increase of hot extremes over land during the so-called global warming hiatus. This tendency is greater for the most extreme events and thus more relevant for impacts than changes in global mean temperature. Graphic: Seneviratne, et al., 2014 / doi:10.1038/nclimate2145

By Sonia I. Seneviratne, Markus G. Donat, Brigitte Mueller, and Lisa V. Alexander   
26 February 2014

(Nature Climate Change) – Observational data show a continued increase of hot extremes over land during the so-called global warming hiatus. This tendency is greater for the most extreme events and thus more relevant for impacts than changes in global mean temperature.

Trends in hot extremes over land vs trends in mean temperature over land 

The signal identified in the trends of hot temperature extremes over land is partly due to an overall larger warming of the mean temperature over land compared to the evolution of the mean global (land + oceans) temperature (Suppl. Figures S3 and S4). This result is consistent with the identified large heat uptake in the oceans (and overall cooling tendencies in sea surface temperatures). Supplementary Fig. S4 shows that it is also identified in a range of datasets (ERA-Interim, HadCRUT4 / CRUTEM4, and the two recently compiled datasets of Cowtan and Way (2014)7), and that the overall tendencies over land are similar for the different datasets.

However, as seen in Suppl. Fig. S3, there is a distinct additional warming of extremes compared to the mean land temperatures. This feature is also seen in geographical maps of trends (Suppl. Fig. S5) with a particular strong signal in mid-latitude regions (excess warming in eastern Europe, part of North America, and South America; lack of cooling in continental Asia), as well as in Greenland. [more]

No pause in the increase of hot temperature extremes

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