The deadly heat waves that began across Central America last month and moved up into Mexico and the Southwestern United States were made 35 times more likely by human-caused climate change, according to a new report by World Weather Attribution, an international organization of climate scientists.
Globally, heat waves are becoming more frequent, longer and hotter as levels of greenhouse gases in the atmosphere rise from the burning of fossil fuels for energy. This week, wide swaths of the United States have been experiencing record-breaking heat and dozens of people have died amid intense heat during this year’s hajj pilgrimage.
“The results of our study should be taken as another warning that our climate is heating to dangerous levels,” Izidine Pinto, a researcher at the Royal Netherlands Meteorological Institute who worked on the analysis, said in a statement.
The scientists examined temperature data from five days of the hottest daytime and nighttime temperatures between late May and early June and compared recorded temperatures with a hypothetical planet in which humans had never pumped any greenhouse gases into the atmosphere.
The extreme heat the scientists studied was caused by a heat dome, where clear, sunny skies radiated the hot air trapped near the ground by a high-pressure weather system. The excessive temperatures were exacerbated by feedback loops caused by an ongoing drought, particularly in Mexico, and warmer ocean temperatures in the Pacific Ocean and the Caribbean.
“This essentially is the same dome of high pressure that started over Central America, ballooned to the Southwest, and now is over the Eastern side of the U.S.,” said Shel Winkley, a meteorologist and weather and climate engagement specialist with Climate Central, a climate communications nonprofit.
This level of heat used to be a once-in-a-lifetime occurrence back in 2000, but with the amount of warming that has happened since then, the average person could experience such an event five or six times in their life.
Heat across the region included in the report caused wildfires, power outages and a mass die-off of endangered monkeys. Dangerous temperatures in Mexico have caused at least 125 deaths since March, according to the study, along with more than 2,300 cases of heat stroke.
The report was released after Mexico recorded its hottest day ever, when temperatures peaked at 125 degrees Fahrenheit in the Sonoran Desert. Temperature records were also broken in Guatemala and Honduras, along with Mexico City, Las Vegas, Phoenix and Death Valley in California.
“Heat deaths are often underestimated,” said Karina Izquierdo, the urban adviser for Latin America and the Caribbean from the Red Cross Red Crescent Climate Center and a contributor to the report.
Heat-related deaths tend to be confirmed months after the heat event, if they are reported at all. Yet, heat is the No. 1 weather-related killer, and dozens of environmental and labor groups are pushing the Federal Emergency Management Agency to declare heat a major disaster.
Some of the groups at greatest risk include agricultural laborers, construction workers and street vendors who face direct exposure, Ms. Izquierdo said, along with unhoused people, pregnant people, young children and older adults.
She said, “Refugees and migrants in transit are particularly vulnerable due to the long and physically demanding journey,” which includes exposure to high temperatures. Between May 31 and June 10, eight bodies of possible migrants were found in the borderlands of southern New Mexico and West Texas, while the region was experiencing excessive heat.
