Fossil fuels making deadly heat waves 'very common' worldwide: Research

The heat wave that killed 125 people in Mexico earlier this month is a harbinger of a warming climate, a new report has found.

In May, a heat dome baked North America from the southwestern U.S. and down into Honduras — just weeks before another heat dome settled over the U.S. Northeast.

But what was once an extreme heat wave is increasingly becoming something more: normal life. 

As fossil fuel burning drives up average temperatures, the heat waves that have struck around the globe in previous months will become "very common," World Weather Attribution Initiative (WWAI) found in a report published Thursday.

The WWAI report came out as a Juneteenth heat wave shatters records from Chicago to the Northeast — bringing to usually temperate northern latitudes the brutal temperatures previously experienced farther south.

Since 2000, fossil fuel emissions have risen almost 50 percent, from 25 billion metric tons of carbon dioxide per year to a current, record rate of 37 billion.

In many parts of the U.S., production remains at record levels, and carbon dioxide levels in the atmosphere are rising faster than ever.

Heat is the deadliest of the weather disasters: In 2023, the hottest year on record, 2,300 Americans died of heat exposures. More than 70 percent of workers worldwide are exposed to heat risks.

“It’s an oven here; you can’t stay here,” 82-year-old Margarita Salazar Pérez of Veracruz, Mexico, told The Associated Press, of the May heat wave.

Before summer had even officially begun, a site in the Sonoran Desert registered Mexico's hottest-ever temperature, 125 degrees Fahrenheit.

The reports find the prime cause in these disasters is the burning of fossil fuels, which leave planet-heating waste products in the atmosphere for centuries.

That dynamic means that over the long term, respite is nowhere in sight.

This year will likely either tie or unseat 2023 for the title of world's hottest year — a general trend of warming punctuated by dramatic, deadly heat waves that WWAI research finds has been made hotter and more likely in a warming world.

Fossil fuel burning drove heat indices across southeast Africa above 122, and in some areas above 140 — in February.

Climate change also powered the April heat wave that led to mass graves in Mali during the Ramadan fast.

And greenhouse gas emissions also drove the May extreme heat wave that withered crops and drove children from schools across Asia.

The team also found that the heat waves that baked much of the globe in July 2023 would have been "virtually impossible" without the planetary heating caused by burning fossil fuels.

Assessing the role of climate change in natural disasters is tricky: Weather is naturally variable, and deadly heat waves happened long before the industrial burning of fossil fuels.

That's where WWAI comes in: a worldwide team of scientists based out of the U.K.'s Imperial College London.

WWAI uses a combination of real-world data and computer modeling to answer one of the most common questions after modern weather disasters: Was this event caused by climate change?

The answer is, increasingly, a resounding yes.

Take Mexico's heat wave earlier this month, for example. That report found that the brutal heat dome that hovered over northern and Central America in early June should happen every 15 years in today's climate.

That's four times as often as in the comparatively cooler climate of 2000.

“From a sort of weather perspective in that sense it wasn’t rare, but the impacts were actually really bad,” Imperial College researcher and WWAI coordinator Friederike Otto told The Associated Press (AP) in an interview.

“The changes we have seen in the last 20 years, which feels like just yesterday, are so strong,” Otto told the AP.

That time, she said, feels "sort of far away and a different world.”

The five-day "maximum temperature event" boosted daytime temperatures an average of 2.5 Fahrenheit above what they would have been without climate change — and made the heat wave itself 35 times more likely.

Like many of the other heat waves tracked by WWAI around the world, Mexico's heat wave was made particularly deadly by the fact that temperatures didn't cool off at night — a time that generally provides respite for bodies stressed by the day's heat.

Mexico's nighttime temperatures — which the report noted no longer counted as extreme under today's climate conditions — were made 200 times more likely by climate change.

In many areas struck by the heat, those nighttime temperatures would have come once in a thousand years.

Over the long term, scientists argue that the only solution to the rising heat is to stop burning fossil fuels. But over the short term, WWAI argues, there is little to do but learn to live with heat.

For outdoor workers, they called for the implementation of heat safety protection laws. For everyone else, they urged investment in resilient grids and water conservation, to avoid deadly blackouts or dehydration.

"Improved urban planning, more green spaces, and enhanced infrastructure in informal settlements will also help protect the most vulnerable," the authors added.