Heat waves today are lasting significantly longer than in the 1980s

An analysis of all heatwaves around the world between 1979 and 2020 found that they now last an average of 12 days, compared to eight days at the start of the study.

As the Earth continues to heat, they will last even longer, says Zhang Wei at Utah State University. “Based on trends, by around 2060 it could double to 16 days,” he says.

Zhang’s team found that heat waves not only last much longer, but also become more frequent and progress more slowly. This means that certain locations have to endure heat wave conditions more frequently and for longer.

Although heat waves are typically thought of as phenomena that affect one region, the areas affected by heat waves change over time as the weather systems responsible for the hot conditions move.

According to the research team, the speed of heat waves has slowed from around 340 kilometers per day in the 1980s to around 280 kilometers per day today. Moreover, the rate of deceleration is accelerating.

Because heat waves last longer, they reach farther, albeit at lower average speeds, increasing the total distance from about 2,500 kilometers to about 3,000 kilometers. This means that a wider area is affected.

The study did not consider the causes of this trend. However, with global warming, heat waves will become more frequent, slower moving, and last longer, meaning they will be more devastating to society and nature than ever before, unless action is taken to prevent further warming. The research team warns that this could have a negative impact.

Most previous studies on heat waves focused on specific locations or regions. Zhang’s team is one of the few that can observe how heat waves move over time.

To do this, the team divided the world into grids. A heat wave is defined as one or more grid rectangles that significantly exceed the average temperature from 1981 to 2010, specifically, temperatures exceeding 95 percent of the temperatures for that period for three or more days. it was done.

The research team found that heat waves tend to move in certain directions depending on prevailing conditions. For example, heat waves in Australia tend to move more south-east, while in Africa they tend to move west.

“I think it’s really interesting to be able to see all the properties of heat waves that you can’t capture if you consider them statically,” he says. andrea beenish He was involved in one of the few other studies at the Ludwig-Maximilians University in Munich, Germany. Seeing heat waves as moving systems.

But when thinking about what we need to do to adapt to a hotter world, regional assessments can be more helpful than global ones, Beinisch says.

She also points out that, for example, heatwave persistence numbers depend largely on how the team defines a heatwave. Even with different definitions, the overall trend remains the same, but the numbers can change significantly. “This needs to be taken into account when looking at the exact numbers,” she says.

Other studies also show that hurricanes move more slowly, he says. david keelings at the University of Florida.

“In short, this means that these incredibly dangerous events last longer in one place and the impact is felt more strongly. In general, the longer a population is exposed to heatwave conditions, the more likely they are to be hospitalized. higher rates and higher mortality rates,” he says.