Dangerous heat will become more common this century

Recently, record-breaking heat waves have occurred in many parts of the world, from Delhi to the Pacific Northwest. To estimate the frequency and severity of such extreme events in the near future, a team of experts from the University of Washington (UW) and Harvard University has analyzed a range of possible heat impacts worldwide by the end of this century, depending on future greenhouse gas emissions. 

“The record-breaking heat events of recent summers will become much more common in places like North America and Europe,” reported study lead author Lucas Vargas Zeppetello, who conducted the research as a doctoral student at the UW and is currently a postdoctoral researcher in Atmospheric Sciences at Harvard. 

“For many places close to the equator, by 2100 more than half the year will be a challenge to work outside, even if we begin to curb emissions. Our study shows a broad range of possible scenarios for 2100. This shows that the emissions choices we make now still matter for creating a habitable future.”

Instead of using the four future emission pathways elaborated by the Intergovernmental Panel on Climate Change (IPCC), the scientists employed a probability-based method to calculate the range of possible future climate conditions. Their statistical approach combined historical data with population projections, economic growth, and carbon intensity (the amount of carbon emitted for each dollar of economic activity) to predict the future possible emissions. After translating the future CO2 levels in a range of global temperature increases, they examined how that would affect monthly weather patterns.

“The number of days with dangerous levels of heat in the mid-latitudes — including the southeastern and central U.S. — will more than double by 2050,” said study co-author David Battisti, a professor of Atmospheric Sciences at the UW. “Even for the very low-end estimates of carbon emissions and climate response, by 2100 much of the tropics will experience ‘dangerous’ levels of heat stress for nearly half the year.”

In the worst-case scenario in which emissions continue unchecked, “extremely dangerous conditions,” in which people would not be able to spend any time outdoors, could become common in regions close to the equator, such as India or Sub-Saharan Africa.

“It’s extremely frightening to think what would happen if 30 to 40 days a year were exceeding the extremely dangerous threshold. These are frightening scenarios that we still have the capacity to prevent. This study shows you the abyss, but it also shows you that we have some agency to prevent these scenarios from happening,” Dr. Vargas Zeppetello concluded.

The study is published in the journal Communications Earth & Environment. 

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By Andrei Ionescu, Earth.com Staff Writer