Present day global warming, most likely caused by human activity, is responsible for about 18% of heavy precipitation and 75% of hot temperature extremes worldwide, reports a paper published online in Nature Climate Change. This proportion is shown to increase with further warming; for example modelling indicates that if temperatures increase to 2 °C higher than pre-industrial levels, about 40% of precipitation extremes will be a result of human influence.

Erich Fischer and Reto Knutti use two metrics to determine what proportion of global high temperature and heavy precipitation events can be attributed to human influence. The metrics are applied to daily outputs from 25 climate models considering 1901-2005 historical simulations and 2006-2100 projections with a high-emission scenario. The authors suggest that the rarest and most extreme events are likely to be more heavily influenced by greenhouse-gas emissions. They note that using a global perspective allows more robust estimates of the effect of warming on extreme events than efforts focusing on single events, where modelling uncertainties can be large.

In an accompanying News & Views, Peter Stott points out that the study can “provide maps of how probabilities of extreme temperatures and precipitation have changed across the globe, [however] the framework they use means that such probabilities cannot be applied to specific individual extreme weather events.”