Poll workers. Pilgrims. Tourists on a hike.

All have died in blistering heat in recent weeks around the world, a harrowing reminder of the global dangers of extreme weather as a severe heat wave bears down on more than 70 million Americans this week.

Dozens of cities in Mexico broke heat records in May and June, killing more than 100 people. India has been under an extraordinarily long heat wave that killed several election workers, and this week, in the capital, Delhi, even overnight temperatures remained in the mid-90s Fahrenheit, or in the mid-30s Celsius. Greece is bracing for wildfires this week, right after back-to-back heat waves killed several tourists. In Bamako, the capital of Mali, hospitals reported more than 100 excess deaths on the first four days of April, The Associated Press reported.

Between May 2023 and May 2024, an estimated 6.3 billion people, or roughly 4 out of 5 people in the world, lived through at least a month of what in their areas were considered abnormally high temperatures, according to a recent analysis by Climate Central, a scientific nonprofit.

The damage to human health, agriculture and the global economy is just beginning to be understood.

Extreme heat killed an estimated 489,000 people annually between 2000 and 2019, according to the World Meteorological Organization, making heat the deadliest of all extreme weather events. Swiss RE, the insurance-industry giant, said in a report this week that the accumulating hazards of climate change could further drive the growing market for insurance against strikes and riots. “Climate change may also drive food and water shortages and in turn civil unrest, and mass migration,” the report said.

As for the world’s two rival economic powers, China and the United States, both face a common peril this summer. As one-fifth of all Americans were under an extreme-heat alert this week, several areas in China’s north broke maximum temperature records. And earlier in the week the capital, Beijing, was under a heat alert as temperatures reached 99 degrees Fahrenheit (37 degrees Celsius).

The two countries are also the two biggest producers of greenhouse gases warming the planet. China’s current emissions are by far the highest in the world, and the United States’ cumulative emissions over the past 150 years of industrialization are the highest in the world.