Magnitude of extreme heat waves in present climate and their projection in a warming world

TLDR

Extreme heat waves, such as the 2010 Russian event that was the strongest globally in recent decades, have serious human and ecosystem impacts, yet prior studies have not compared their magnitude across continents and time. The study introduces a new Heat Wave Magnitude Index that enables cross‑regional and temporal comparisons of heat wave intensity. The index classifies the strongest heat waves worldwide from 1980–1990, 1991–2001, and 2002–2012 using daily maximum temperatures, and multimodel CMIP5 ensemble outputs are employed to project future heat wave occurrence and severity under various IPCC AR5 RCP scenarios. Results indicate that the global area affected by heat waves has risen in recent decades, and CMIP5 projections predict that by the end of the century, under the most severe IPCC AR5 scenario, extreme heat waves comparable to the 2010 Russian event will become the norm, occurring roughly every two years in regions such as southern Europe, North America, South America, Africa, and Indonesia.

Abstract

Abstract An extreme heat wave occurred in Russia in the summer of 2010. It had serious impacts on humans and natural ecosystems, it was the strongest recorded globally in recent decades and exceeded in amplitude and spatial extent the previous hottest European summer in 2003. Earlier studies have not succeeded in comparing the magnitude of heat waves across continents and in time. This study introduces a new Heat Wave Magnitude Index that can be compared over space and time. The index is based on the analysis of daily maximum temperature in order to classify the strongest heat waves that occurred worldwide during the three study periods 1980–1990, 1991–2001, and 2002–2012. In addition, multimodel ensemble outputs from the Coupled Model Intercomparison Project Phase 5 are used to project future occurrence and severity of heat waves, under different Representative Concentration Pathways, adopted by the Intergovernmental Panel on Climate Change for its Fifth Assessment Report (AR5). Results show that the percentage of global area affected by heat waves has increased in recent decades. Moreover, model predictions reveal an increase in the probability of occurrence of extreme and very extreme heat waves in the coming years, in particular, by the end of this century, under the most severe IPCC AR5 scenario, events of the same severity as that in Russia in the summer of 2010 will become the norm and are projected to occur as often as every 2 years for regions such as southern Europe, North America, South America, Africa, and Indonesia.