Heat waves that spark damaging droughts are happening more frequently, study finds

WASHINGTON (AP) — Heat waves that lead to sudden and damaging drought are spreading across the globe at an accelerating rate, highlighting how climate change-fueled extremes can build dangerously off each other, a new study found.

Researchers from South Korea and Australia looked at compound extreme weather — a one-two punch of heat and drought — and found it increasing as the world warms. But what's rising especially fast is the more damaging type when the heat comes first and that triggers the drought. In the 1980s, that kind of extreme covered only about 2.5% of Earth's land each year. By 2023, the last year the researchers studied, it was up to 16.7%, with a 10-year average of 7.9%

The average has likely gone even higher with 2024's record global heat and a 2025 that was nearly as warm, the study's authors said.

In their study published in Friday's Science Advances, the scientists said the quickening rate of change is even more concerning than the raw numbers. For about the first two decades since 1980 they examined, the spread of heat-first extremes increased, but the rate in the last 22 years is eight times higher than the earlier rate, the study found.

Events where drought happens first, followed by high heat, remain more common and are also rising. But the researchers focused on those increasing cases where heat struck first. That's because when heat strikes first, the droughts are stronger than when the droughts come first or don't come with high heat, said co-author Sang-Wook Yeh, a climate scientist at Hanyang University in South Korea.

They also lead to "flash droughts,'' which are more damaging than ordinary droughts because they come on suddenly, not allowing people and farmers to prepare, said lead author Yong-Jun Kim, a Hanyang climate scientist.

Flash droughts — when warmer air gets thirstier it sucks more water out of soil — have been increasing in a warming world, past studies show.

“The study illustrates a key point about climate change: the most damaging impacts often come from compound extremes. When heat waves, drought, and wildfire risk occur together — as we saw in events like the Russian heat wave of 2010 or the Australian bushfires in 2019-20 — the impacts can escalate quickly,” said Andrew Weaver, a climate scientist at the University of Victoria in British Columbia, Canada. “What this study shows is that warming doesn’t just make heat waves more likely — it changes how heat and drought interact, amplifying the risks we face."

Weaver was not part of the study, but he lives in the Pacific Northwest, where the 2021 heat dome and drought was what Kim called a top example of what they see rapidly increasing. Others include the 2022 heat and drought around China's Yangtze River and the 2023-24 record heat and drought in the Amazon, Kim said.

“The 2021 Pacific Northwest heat dome illustrates how quickly these compound extremes can escalate — temperatures near 50°C (122 degrees Fahrenheit) in Lytton (British Columbia) were followed by rapid drying and extreme wildfire conditions that destroyed the community,” Weaver, a former Canadian legislator, said in an email.

The study found the biggest increases in heat-first droughts in South America, western Canada, Alaska and the western United States, and parts of central and eastern Africa.

Kim and Yeh said they noticed a “change point” around the year 2000, when everything sped up for heat-then-drought situations.

Jennifer Francis, a Woodwell Climate Research Center climate scientist who wasn’t part of the study, said that change point was “eerily coincident with the onset of rapid Arctic warming, sea-ice loss, and decline in spring snow cover on Northern Hemisphere continents.”

In addition to long-term warming causing more compound extremes, Kim said they saw a speeding-up in the way heat went from land to air and back again just before that 2000 change point. He and Yeh speculated that Earth may have crossed a “tipping point" where the change is irreversible.

Several aspects of Earth's climate and ecological systems changed in the late 1990s, with a possible trigger by a major El Nino event in 1997-98, said Gerald Meehl, a climate scientist at the National Center for Atmospheric Research who wasn't part of the study. But he added that it's hard to tell whether they are permanent changes.

Some computer models forecast another major El Nino — a natural warming of parts of the Pacific that warp weather worldwide — brewing later this year.

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FILE - Fire burns in a field of grass near Bumbalong, south of the Australian capital, Canberra, Feb. 1, 2020. (AP Photo/Rick Rycroft, File)

FILE - Residents of a riverside community carry food and containers of drinking water after receiving aid due to the ongoing drought in Careiro da Varzea, Amazonas state, Brazil, Oct. 24, 2023. (AP Photo/Edmar Barros, File)

FILE - People prepare to swim in the Yangtze River near a bridge support column that shows previous water levels in southwestern China's Chongqing Municipality, Aug. 19, 2022. (AP Photo/Mark Schiefelbein, File)

FILE - Students carrying umbrellas stand on the dry riverbed of the Jialing Rivera, a tributary of the Yangtze, in southwestern China's Chongqing Municipality, Aug. 19, 2022. (AP Photo/Mark Schiefelbein, File)

FILE - A resident of a riverside community carries food and containers of drinking water after being distributed due to the ongoing drought in Careiro da Varzea, Amazonas state, Brazil, Oct. 24, 2023. (AP Photo /Edmar Barros, File)

JERUSALEM (AP) — Satellite images, expert analysis, a U.S. official and public information released by the U.S. and Israeli militaries suggest an explosion that killed scores of Iranian students at a school was likely caused by U.S. airstrikes that also hit an adjacent compound associated with the regime's Revolutionary Guard.

The Feb. 28 strike, which had the highest reported civilian death toll since the war began, has come under staunch criticism from the United Nations and human rights monitors. More than 165 people were killed, most of them of children, in the blast during school hours at Shajareh Tayyebeh Elementary School, according to Iranian state media.

Satellite images taken Wednesday and reviewed by the The Associated Press show most of the school in the city of Minab, some 1,100 kilometers (680 miles) southeast of Tehran, reduced to rubble, a crescent shape punched into its roof. Experts say the tight pattern of the damage visible on the satellite photos is consistent with a targeted airstrike.

Iran has blamed Israel and the United States for the blast. Neither country has accepted responsibility. Asked about the strike at the school at a Pentagon press briefing Wednesday, Defense Secretary Pete Hegseth said, “All I can say is that we’re investigating that. We, of course, never target civilian targets. But we’re taking a look and investigating that.”

Several factors point to a U.S. strike.

One is the launching of an assessment of the incident by the U.S. military. According to the Pentagon's instructions on processes for mitigating civilian harm, an assessment is launched after a group of investigators make an initial determination that the U.S. military may bear culpability. A U.S. official told the AP that the strike was likely U.S. The official spoke anonymously because they were not authorized to comment publicly on the sensitive matter.

Another is the location of the school — next to a base of the Revolutionary Guard in Hormozgan Province and close to a barracks for its naval brigade. The U.S. military has focused on naval targets and acknowledged strikes in the province, including one in the vicinity of the school.

Israel, which has denied conducting the strike, has focused on areas of Iran closer to Israel and hasn’t reported conducting any strikes south of Isfahan, 800 kilometers (500 miles) away. The U.S. is operating warships in the Arabian Sea, including the USS Abraham Lincoln aircraft carrier, within range of the school.

When asked by the AP about its findings, U.S. military Central Command spokesperson Capt. Tim Hawkins said, “It would be inappropriate to comment given the incident is under investigation.”

White House press secretary Karoline Leavitt told reporters Friday that she had no updates on the investigation and did not directly answer a question about whether Trump was satisfied with the pace of the probe.

“My assumption is that probably there were some activities recently there and they detected and tracked them, but ... they weren't aware or didn't have an up-to-date database that a girls' school was there and they bombed it," said Farzin Nadimi, a senior fellow at the Washington Institute for Near East Policy who studies Iran’s military.

The school is adjacent to a walled compound labeled on maps as the Seyyed Al-Shohada Cultural Complex of the Guard, which included a pharmacy, gym and sports field.

In addition to the school, satellite photos show that blasts struck at least five buildings in the Guard compound, leaving the area pocked with craters, charred holes in roofs and piles of rubble.

Iranian online map applications show a living quarters for the Assef Brigades about 150 meters (165 yards) from the school, inside the Revolutionary Guard compound. The 16th Assef Coastal Missile Group is part of the Guard's navy, Nadimi said. The 1st Naval District, which the Assef Brigades belong to, is responsible for the Strait of Hormuz, the narrow mouth of the Persian Gulf through which a fifth of all oil and natural gas traded passes. The strait has been a particular point of conflict in the war.

In the aftermath of the strike, video from Iran's state broadcaster verified by the AP using satellite imagery showed dozens of fresh graves dug at a nearby cemetery. Nadimi said it is likely the school taught daughters of Guard personnel.

The strike has drawn wide condemnation from the secretary-general of the United Nations and international human rights groups. The criticism comes amid reports that airstrikes have also hit other schools in Iran.

Targeting schools would be a clear violation of international laws governing armed conflict, said Elise Baker, a senior staff lawyer at the Atlantic Council, a Washington-based nonprofit think tank.

“Strikes can only legally target military objectives and combatants, but the school was a civilian object and the students and teachers were civilians,” Baker said. “The school’s proximity to (Guard) facilities and the attendance of children of (Guard) members at the school does not change that conclusion: It was a civilian object.”

Three experts told the AP the satellite imagery and videos from the scene strongly suggested multiple munitions hit the compound. Complicating any assessment is the lack of images of bomb fragments from the blast. No independent agency has reached the site during the war to investigate.

There are no craters or evidence of bombs hitting in the surrounding neighborhood, suggesting a great degree of accuracy, said Corey Scher, a researcher who uses satellite imagery and radar data to study landscape changes in armed conflict zones.

“All the strikes are clustered within the walled-off compound," Scher said. "That’s one level of precision at the block level. And then most of the strikes are basically leading to direct hits on buildings. That’s another level of precision.”

Scher said the school and the other buildings struck in the compound showed damage consistent with the use of air-to-surface munitions.

“They didn’t explode in the air above the building," he said. “It looks like the explosion happened at the time they hit the surface, whether it was the building or the ground."

Sean Moorhouse, a former British Army officer and explosive ordnance disposal expert, said the available satellite imagery was insufficient to determine exactly what type of munitions were used in the strike, but he said the visible damage was consistent with what would be expected with impacts from multiple 2,000-pound (900-kilogram) high-explosive warheads. He said the multiple precise impacts would undercut any suggestion that a malfunctioning Iranian missile hit the school.

N.R. Jenzen-Jones, the director of Armament Research Services, said the school and Guard compound were targeted with “multiple simultaneous or near-simultaneous strikes." He said in videos of the school taken immediately after the strike, smoke can be seen rising from the Guard compound. There were also impacts on multiple buildings visible in satellite images and media reports citing witnesses who said they heard multiple explosions.

“If indeed it is confirmed that an American or Israeli strike hit the school, there are several potential points of failure in the targeting cycle," Jenzen-Jones said. “We might be seeing an intelligence failure, likely rather early in the process, which misidentified the target or failed to update a targeting list following the building’s change in use.”

Biesecker reported from Washington. Associated Press writers Jon Gambrell in Dubai, United Arab Emirates, Konstantin Toropin and Michelle Price in Washington, and Aamer Madhani in Doral, Florida, contributed to this report.

A Dept. of Defense map entitled, Operation EPIC FURY Timeline - First 100 Hours, is displayed during a news conference with Defense Secretary Pete Hegseth and Chairman of the Joint Chiefs of Staff Gen. Dan Caine, at the Pentagon, Wednesday, March 4, 2026, in Washington. (AP Photo/Konstantin Toropin)