Climatic Change

, Volume 107, Issue 3–4, pp 615–624

Observational and model evidence of global emergence of permanent, unprecedented heat in the 20th and 21st centuries

A letter
Open Access


Given the severe impacts of extreme heat on natural and human systems, we attempt to quantify the likelihood that rising greenhouse gas concentrations will result in a new, permanent heat regime in which the coolest warm-season of the 21st century is hotter than the hottest warm-season of the late 20th century. Our analyses of global climate model experiments and observational data reveal that many areas of the globe are likely to permanently move into such a climate space over the next four decades, should greenhouse gas concentrations continue to increase. In contrast to the common perception that high-latitude areas face the most accelerated response to global warming, our results demonstrate that in fact tropical areas exhibit the most immediate and robust emergence of unprecedented heat, with many tropical areas exhibiting a 50% likelihood of permanently moving into a novel seasonal heat regime in the next two decades. We also find that global climate models are able to capture the observed intensification of seasonal hot conditions, increasing confidence in the projection of imminent, permanent emergence of unprecedented heat.

Supplementary material

10584_2011_112_MOESM1_ESM.eps (712 kb)
(EPS 712 KB)
10584_2011_112_MOESM2_ESM.eps (36.8 mb)
(EPS 36.7 MB)
10584_2011_112_MOESM3_ESM.eps (34.4 mb)
(EPS 34.3 MB)
10584_2011_112_MOESM4_ESM.eps (34.4 mb)
(EPS 34.3 MB)
10584_2011_112_MOESM5_ESM.eps (490 kb)
(EPS 489 KB)
10584_2011_112_MOESM6_ESM.eps (606 kb)
(EPS 606 KB)
10584_2011_112_MOESM7_ESM.eps (13.6 mb)
(EPS 13.5 MB)
10584_2011_112_MOESM8_ESM.eps (13.5 mb)
(EPS 13.5 MB)

Copyright information

© The Author(s) 2011

Authors and Affiliations

  1. 1.Department of Environmental Earth System Science and Woods Institute for the EnvironmentStanford UniversityStanfordUSA

Personalised recommendations