As LA bakes, duration of heat waves is accelerating faster than climate change, UCLA study shows

Clara Harter, Los Angeles Times on Jul 10, 2025

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As sizzling temperatures sweep across Southern California this week, University of California, Los Angeles researchers have released an alarming new finding — the duration of heat waves is increasing faster than global warming itself.

Researchers found that not only are heat waves getting hotter, but they're also becoming longer at a rate that will only further accelerate as the planet continues to warm.

"Each fraction of a degree of warming will have more impact than the last," said UCLA climate scientist David Neelin, who helped lead the study.

This means that even relatively modest warming can significantly boost the risk of powerful, enduring heat waves — underscoring the need to develop strategies to help keep people, agriculture and infrastructure safe in extreme heat, he said.

"If the rate of warming stays the same, the rate of our adaptation has to happen quicker and quicker, especially for the most extreme heat waves, which are changing the fastest," Neelin said in a statement.

In Southern California, longer heat waves will dry out vegetation and increase the danger of wildfires, Neelin said in an interview. Worsening heat waves also pose a serious threat to farming, as many crops will die at sustained high temperatures, he added.

The study was published in Nature Geoscience this week and conducted by researchers from UCLA and the Universidad Adolfo Ibañez in Santiago, Chile, who analyzed historical and projected heat waves around the world.

"We found that the longest and rarest heat waves in each region — those lasting for weeks — are the ones that show the greatest increases in frequency," Cristian Martinez-Villalobos, lead author of the study and an assistant professor of engineering and science at the Universidad Adolfo Ibáñez, said in a statement.

The growing dangers of heat waves can already be seen this summer, the researchers noted, pointing to the late June heat dome that settled over the eastern U.S. and set new daily heat records in at least 50 cities, according to the National Oceanic and Atmospheric Administration.

A heat wave in Europe around the same time led to the deaths of at least 1,500 people, one study concluded, and forced a rare closure of the Eiffel Tower's summit last week.

And this week, a hot spell has descended upon Southern California.

Woodland Hills, Lancaster and Palmdale all broke the 100-degree mark on Wednesday, while Palm Springs hit a scorching 118 degrees, according to the National Weather Service. It's expected to cool down over the weekend, but forecasters predict another round of potentially dangerous heat next Tuesday through Friday.

This pattern of frequent heat waves will become more common around the globe, according to the UCLA study.

Those changes will be harshest in tropical regions of Southeast Asia, South America and Africa that are close to the equator, the study says.

This is because these areas already have hot weather and relatively low temperature variation, so each additional degree of warming will have a noticeable effect. For example, the researchers predicted that heat waves lasting 35 days or longer in equatorial Africa will happen 60 times more often from 2020 to 2044 than they did from 1990 to 2014.

One of the key contributions of the study was the creation of a formula that can ascertain the effects of climate change on temperatures around the globe.

But Neelin said that further research is needed to predict the impact of longer, hotter and more frequent heat waves on variables such as soil moisture and wildfire risk to help urban planners and the agricultural industry prepare. He also highlighted the importance of building high-accuracy weather and climate models to provide the public with timely and accurate heat-related warnings.

Neelin said, however, that this work is imperiled by the Trump administration's cuts to climate change research funding, which is affecting important agencies including NOAA.

"Deprioritizing and defunding climate and science research will limit our capacity to make region-specific projections for risk management," he said. "Without that, we'll have much less ability to adapt to climate change at the very time when we need to accelerate adaptation planning."