Climate change leaves fingerprints on July heat waves around the globe, study says

The fingerprints of climate change are all over the intense heat waves gripping the globe this month, a new study finds. Researchers say the deadly hot spells in the American Southwest and Southern Europe could not have happened without the continuing buildup of warming gases in the air.

Thanks to years of research and more powerful computers, scientists can now determine almost in real-time whether climate change is contributing to the intensity of heat, storms, floods and drought — and by how much.

A generation ago, calculating such connections took up to a year, but researchers at World Weather Attribution made their conclusions about this summer’s heat wave in less than a week. Their study is the first to look at three simultaneous heat waves on three different continents.

These unusually strong heat waves are becoming more common, Tuesday’s study said. The same research found the increase in heat-trapping gases, largely from the burning of coal, oil and natural gas has made another heat wave — the one in China — 50 times more likely.

A stagnant atmosphere, warmed by carbon dioxide and other gases, made the European heat wave 4.5 degrees Fahrenheit (2.5 degrees Celsius) hotter, the one in the United States and Mexico 3.6 degrees Fahrenheit (2 degrees Celsius) warmer and the one in China 1.8 degrees Fahrenheit (1 degree Celsius) toastier, the study found.

Relying on data gleaned from tree rings and other stand-ins for temperature records, several climate scientists say this month’s heat is likely the hottest Earth has been in about 120,000 years, which would make it easily the hottest of human civilization.

The global average temperature has been hotter in 22 of the first 24 days of July than on any other single day recorded, according to calculations by the University of Maine’s Climate Reanalyzer.