Climate equation predicts a rapid rise in extreme heatwaves

Heatwaves aren’t just getting hotter and more frequent – they’re also lasting longer. And the more the planet warms, even by small amounts, the faster those heatwaves will stretch out.

Traditional climate models simulate average conditions over weeks or months. A study, led by UCLA and Universidad Adolfo Ibáñez in Chile adds a new twist.

The research introduces a statistical term that connects one day’s temperature to the next – something scientists refer to as a “memory” of heat.

Climate memory reshapes forecasts

When that feedback was added, the simulations showed a clear global pattern. Heatwaves grow longer at a faster rate with each small increase in background climate temperature.

Study senior author David Neelin, a distinguished professor of atmospheric and oceanic sciences at UCLA, noted that each fraction of a degree of warming will have more impact than the last.

“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 heatwaves, which are changing the fastest,” said Neelin.

“We found that the longest and rarest heatwaves in each region – those lasting for weeks – are the ones that show the greatest increases in frequency,” added lead author Cristian Martinez-Villalobos, a researcher at the Universidad Adolfo Ibañez.

Accounting for local temperature shifts, the team found heatwave durations are already accelerating just as climate models predict.

Warming climate fuels faster heatwaves

Recent headlines bear out the model’s warning. In late June, a heat dome lingered over much of the United States, stretching emergency services and even warping infrastructure such as a Virginia drawbridge.

Europe faced record-setting temperatures during the first week of July. The heat temporarily closed tourist landmarks and triggered Wimbledon’s “Operation Ice Towel.”

Such events highlight the study’s real-world stakes. Longer heatwaves raise health risks, stress power and water systems, reduce crop yields, and increase wildfire threats.

Longest heatwaves in tropics

Not every part of the globe will feel the acceleration equally. In areas where day-to-day temperatures already swing widely, an extra degree of average warmth adds proportionally less strain than it does in regions with relatively stable climates.

“If you have large variations in current climate, then a fraction of a degree change will have less impact than if you have a more stable climate,” Neelin said.

“So impacts in tropical regions tend to be bigger than in temperate regions, and winter warm spells will change less than summer because summer tends to have smaller variability.”

Because of that dynamic, the tropics – and especially equatorial Africa, Southeast Asia, and northern South America – are expected to suffer the most pronounced lengthening of extreme heat.

The analysis suggests that in equatorial Africa, heatwaves exceeding 35 days could become roughly 60 times more common during 2020-2044 than they were in 1990-2014.

Budget cuts stall climate science

Beyond quantifying future risk, the study supplies a mathematical framework that engineers, public-health officials, and wildfire managers can plug into existing risk assessments.

Projections of soil-moisture depletion, for example, feed directly into crop-yield forecasts and fire-weather indices.

However, the authors caution that translating the new insights into action requires sustained investment in climate modeling.

“Addressing those will depend on having high-accuracy weather and climate models, but the current federal budget is putting a pause on the United States’ capabilities and eliminating excellent young scientists from the field,” Neelin said.

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

Heatwaves demand faster action

The research highlights an uncomfortable truth: adaptation timelines must shorten as the planet warms, because the rate at which heatwaves lengthen speeds up with each incremental rise in temperature.

Urban planners drafting heat-action plans today will need to revisit them sooner than expected. Electric-utility managers can’t assume linear growth in demand, and public-health officials must prepare for more frequent multi-week emergencies.

All of that work hinges on reliable, high-resolution climate projections – exactly the kind of scientific endeavor that recent funding cuts threaten.

Whether communities can keep pace with the accelerating hazard may depend as much on political will to support climate science as on any thermodynamic process in the atmosphere.

The study is published in the journal Nature Geoscience.

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