Scientists identify early warning signals of heat waves

When it comes to predicting heat waves, a new study from Arizona State University shows that the necessary data already exists, and simply needed a new approach. The experts found clear patterns in temperature evolution that precede abrupt global warming events.

“Critical transitions have been identified in global and regional climate systems, during which a small perturbation can lead to a qualitative change. They are notoriously difficult to predict and can have potential catastrophic impacts on ecosystems and human society,” wrote the study authors. 

“However, certain characteristics may exist prior to such transitions, and can serve as the early‐warning signals to predict critical transitions in climate systems. Here we investigate the early‐warning signals in global warming and regional heat waves based on temperature records.”

The researchers analyzed temperature records during the early 20th century – before global warming – as well as temperatures leading up to recent heat waves. The analysis revealed clear patterns that can serve as early warning signals of extreme heat waves.

Study co-author Chenghao Wang is a former ASU Research Scientist who is now at the Department of Earth System Science at Stanford University. 

“Many studies have identified such changes in climate systems, like the sudden end of a glacial period,” said Wang. “These qualitative changes usually have early-warning signals several thousand years before them.”

“We detected similar signals in events much shorter than previous studies. We found early-warning signals also exist before global warming and heat waves on the time scale of years and days.”

Beyond looking at historical data, the experts have been tracking current temperature fluctuations based on data from airport weather stations. The researchers explained that when three consecutive days are unusually hot compared to the 30-year record, it is considered a heat wave.

“This method isn’t just applicable for predicting extreme weather events in the next few days or weeks,” said Professor Zhihua Wang. “It observes human-induced variabilities and will support prediction over the next decades or even century.” 

According to Professor Wang, the new analytic method creates a “completely new frontier” for evaluating how things like global energy consumption and, conversely, the introduction of urban green infrastructure, are affecting climate change. 

“We’re not replacing existing evaluation tools. The data is already there. It’s enabling us to gauge what actions are having an impact.”

For their investigation, Chenghao Wang and Professor Zhihua Wang also collaborated with rising high school junior Linda Sun at Horace Greely High School in Chappaqua, New York.

The study is published in the journal Geophysical Research Letters.

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By Chrissy Sexton, Earth.com Staff Writer