Climate change can have a very direct impact on humans. Heatwaves, such as the ones currently experienced in Western Europe and some parts of the continental U.S., can not only cause forest fires and droughts, but also kill people. The human body can tolerate only a narrow range of temperatures, and especially young or elderly people are at risk of death during extreme heat. A European heatwave in 2003 killed approximately 70,000 people, one in Moscow, Russia, in 2010 killed about 10,000 people, and a 1995 heatwave in Chicago, IL, USA, was responsible for around 700 deaths.
Camilo Mora, University of Hawai’i at Mānoa, Honolulu, HI, USA, and colleagues have performed a literature analysis of deadly heatwaves worldwide and projected the number of such occurences in the future. The team found 1,900 locations where heatwaves have killed people since 1980. The researchers used the data to identify a threshold beyond which temperatures and humidities become deadly. Currently, about 30 % of the world’s population is exposed to such deadly conditions for at least 20 days each year.
The team then projected the number of days with potentially deadly conditions a given region will experience in the future. By 2100, the percentage of people subjected to deadly heat for at least 20 days a year is expected to increase to about 48 % in a scenario with drastic reductions of greenhouse gas emissions and to roughly 74 % with growing emissions. Tropical humid areas will be disproportionately exposed to more days with deadly heat. The researchers have also created an interactive website to visualize these results for the public.
- Global risk of deadly heat,
Camilo Mora, Bénédicte Dousset, Iain R. Caldwell, Farrah E. Powell, Rollan C. Geronimo, Coral R. Bielecki, Chelsie W. W. Counsell, Bonnie S. Dietrich, Emily T. Johnston, Leo V. Louis, Matthew P. Lucas, Marie M. McKenzie, Alessandra G. Shea, Han Tseng, Thomas W. Giambelluca, Lisa R. Leon, Ed Hawkins, Clay Trauernicht,
Nat. Clim. Change 2017.