Heat Waves Could Increase Substantially in Size by Mid-Century

Our planet has been baking under the sun this summer as temperatures reached the hottest ever recorded and heat waves spread across the globe.  While the climate continues to warm, scientists expect the frequency and intensity of heat waves to increase.  However, a commonly overlooked aspect is the spatial size of heat waves, despite its important implications. 

For the first time, in a new study, scientists funded in part by the NOAA Climate Program Office’s Climate Observations and Monitoring Program examined this aspect under two different scenarios.  They found that by mid-century, in a middle greenhouse emissions scenario, the average size of heat waves could increase by 50%.  Under high greenhouse gas concentrations, the average size could increase by 80% and the more extreme heat waves could more than double in size.

“As the physical size of these affected regions increases, more people will be exposed to heat stress,” said Brad Lyon, Associate Research Professor at the University of Maine and lead author of the new paper published in Environmental Research Letters.  “Larger heat waves would also increase electrical loads and peak energy demand on the grid as more people and businesses turn on air conditioning in response.”

In addition to heat wave size and exposed population, the authors found that related attributes like duration, magnitude, and cooling degree days (a measure for energy use) could increase substantially.  However, Lyon noted that these results were not particularly surprising.

“An increase in attributes like magnitude and duration is consistent with expectations of a warming climate,” said Lyon.  “What is new in our study is the way we calculated them, which allowed us to consider size as a new heat wave dimension.”

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