Study finds one to two additional months of heat stress since 1970s in several countries

A study published Monday in the journal Nature Climate Change found that several countries are experiencing one to two additional months of heat stress compared with the 1970s. Researchers examined feels-like temperatures that account for humidity, wind speed and other factors rather than air temperature alone.

The analysis used the Universal Thermal Climate Index to categorize heat stress as strong at 32 degrees Celsius or higher, very strong at 38 degrees Celsius or higher, and extreme at 46 degrees Celsius or higher. Parts of Southern Africa, Eastern Africa, Mexico and Central America recorded roughly 50 more days per year of at least strong heat stress than in the 1970s.

Regional changes documented Southern Europe showed increases of up to 40 additional days of strong heat stress in areas of Spain, Italy, Greece and Turkey. Much of the United States recorded at least 15 more days of strong heat stress, with southern states including Texas and Florida seeing close to 25 additional days of very strong heat stress.

The study also reported that the ten warmest nights of each year have warmed faster than the ten warmest days, rising 0.32 degrees Celsius per decade compared with 0.27 degrees Celsius per decade. This change means minimum overnight temperatures more often exceed 20 degrees Celsius, limiting recovery from daytime heat.

Population exposure and future outlook One billion more people now face at least one day of extreme heat stress each year than in the 1970s. Regions that previously recorded no heat stress days are now experiencing them. The study’s lead author stated that the findings highlight the need for mitigation of future warming along with adaptation measures such as heat health action plans and early warning systems.