Science

Heatwaves are becoming more frequent, moving slower, and lasting longer

Utah Public Radio | By Ryan Helcoski

Published May 13, 2024 at 12:54 PM MDT

Three graphs visually demonstrate how heatwaves have changed over time. The graphs indicate that globally, heatwaves are becoming more frequent, they are also covering larger areas and moving across those areas at a slower speed, meaning they are lasting longer.

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Globally, heatwaves are becoming more frequent (A). They are also covering larger areas (B) and moving across those areas at a slower speed (C), meaning they are lasting longer. A possible mechanism behind this is examined in (D) and explained more in the team's paper "Anthropogenic forcing has increased the risk of longer-traveling and slower-moving large contiguous heatwaves" that appears in Science Advances.

Science Advances

Wei Zhang, researcher and assistant professor of climate science at Utah State University, stands in front of a large staircase.

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Wei Zhang, assistant professor of climate science at Utah State University

Wei Zhang

A heatwave, or extreme heat, is a period of abnormally hot weather. They are often measured relative to the usual climate and seasonal variations in a given location and they can sometimes cover a very large area.

“So those extreme temperatures across a large region could have huge impacts on health and on the environment,” said Wei Zhang.

Zhang is an assistant professor of climate science at USU. He is part of an international team who discovered that globally, heatwaves are becoming more frequent, lasting longer and moving slower, covering larger areas, and becoming even hotter.

“That is not good news,” he said.

Not only that, but globally, these changes have amplified since 1997. For example, from 2016 to 2020, the average heatwave lasted 12 days. That’s four days longer than the average of eight from 1979 to 1983.

These heatwaves also cover ever larger areas and have been increasing at a rate of an additional 8.3 events per decade. This does vary by location, but globally they will become more extreme in the near and distant future.

A map of the world showing the global distribution of heatwaves with sizes and colors that indicate their area and relative intensity. The map has numerous circles all around it, indicating a wide spread of heatwaves. However, the brightest red marks (the most intense heatwaves) are located further away from the poles, meaning that heatwave area and intensity changes with latitude. — Global distribution of heatwaves with sizes and colors that indicate their area and relative intensity. The graph to the right summarizes how their area and intensity changes with latitude.

However, though the results are dire, Zhang doesn’t see this as simply more to worry about. As a climate scientist, he’s used to dealing with difficult results.

“I mean, many of my studies don't produce good news," said Zhang. "But it is what it is.”

He points out that though this is the reality of our present, we can still change our future.

“We have adaptation and mitigation to better adapt ourselves to this extreme heat. For example, you know, we could plant more trees, right, we could build green infrastructure, green roofs, green walls to reduce the heat in the city. And we could also be adding more cooling centers,” he said.

That’s significant because Zhang’s study focused primarily on our past and a future under rising greenhouse gas emissions without effective climate action. But that doesn’t have to be our future. As Zhang himself emphasizes, this study and others like it can guide our choices going forward.

“What we can do is to better adapt ourselves," said Zhang. "And, if possible, do more mitigation to cut carbon emissions so that we could have less extreme heat in the future.”