Extreme heat waves are becoming longer and more frequent

A study on abnormal heat phenomena, involving researchers from the United States and Chile, reveals an acceleration of the trend on a global scale. Tropical regions are the most affected

di Matteo Cavallito

 

Heatwaves, especially the most extreme ones, are expected to have an increasing impact globally, particularly in tropical regions.
This is the conclusion of a recent study conducted by the University of California, Los Angeles (UCLA), and the Universidad Adolfo Ibáñez in Santiago, Chile.

The research, published in the journal Nature Geoscience, specifically finds that longer heat periods will experience the greatest acceleration, and the frequency of the most intense events will increase most significantly—posing greater risks to people, animals, agriculture, and ecosystems.

The phenomenon is accelerating

“The probability distributions of heatwave durations are shaped by day-to-day correlations in temperature and so cannot be simply inferred from changes in the probabilities of daily temperature extremes,” the study explains. To address this, the researchers developed an equation that enables the analysis of the phenomenon on a regional scale or across multiple regions.

By incorporating variables into climate models that account for how each day’s temperature influences the next, the study—according to a statement from UCLA—identified a trend acceleration on a global scale.

“Here we show from statistical analysis of global historical and projected temperature data that changes in long-duration heatwaves increase nonlinearly with temperature.”

More frequent extreme heatwaves

“Each fraction of a degree of warming will have more impact than the last,” said David Neelin, a climatologist at UCLA and co-author of the study. “The acceleration means that 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.”

Specifically, the authors continue, “We show that the curve for this acceleration can be approximately collapsed onto a single dependence across regions by normalizing by local temperature variability.” Moreover, they note, “the longest, most uncommon heatwaves for a given region have the greatest increase in likelihood.”

Tropical regions are the most affected

The growing intensity and frequency of heat and drought events as a result of climate change have long been known. However, the study has revealed some specific dynamics that had not yet been analyzed. Among them is the trend for seasons and locations that currently show lower weather variability to undergo the most significant changes.

In tropical regions, where summer temperatures are typically less variable than in temperate zones. For example, heatwaves will have a greater impact. “Southeast Asia and the equatorial regions of South America and Africa will likely see some of the greatest impacts,” the statement explains. “The research projected that heat waves in equatorial Africa lasting more than 35 days would happen a whopping 60 times more often in the near future (2020 to 2044) compared with the recent past (1990 to 2014).”