World to See 57 More Extreme Heat Days Yearly by 2100

The research, conducted by World Weather Attribution and U.S.-based Climate Central, found that global efforts to cut greenhouse gas emissions under the 2015 Paris Agreement have significantly curbed the rise in extreme heat. Without those efforts, the world would be heading toward 114 additional “superhot” days each year — twice the number now projected.

Using advanced computer simulations, scientists compared global and country-level data from 2015, current conditions, and two future scenarios — one where nations meet their current climate pledges and another reflecting the path the world was on before the Paris accord.

If countries honor their pledges and global temperatures rise by 2.6 degrees Celsius above preindustrial levels by 2100, Earth would experience 57 more superhot days annually than today, the study said. Without the Paris Agreement, the projected 4-degree Celsius rise would double that number.

'There will be pain and suffering'

“There will be pain and suffering because of climate change,” said Kristina Dahl, Vice President for Science at Climate Central and co-author of the report. “But if you compare 4 degrees of warming with 2.6 degrees, that difference reflects a decade of global efforts — and that’s encouraging.”

Nearly 200 countries are set to meet next month in Brazil for another round of global climate talks. Experts say the new findings illustrate both the progress and the shortcomings of the Paris Agreement — a historic step that slowed warming but still falls short of preventing widespread harm.

Victor Gensini, a climate scientist at Northern Illinois University, said the data “highlight both the success and the shortfall of the Paris Agreement.”

Since 2015, the world has already seen an average of 11 more superhot days each year, defined as days hotter than 90% of comparable dates between 1991 and 2020.

“That heat sends people to emergency rooms. Heat kills,” Dahl said.

Billions at risk

Although the report does not estimate the total number of people who will be affected, Friederike Otto of Imperial College London, another co-author, said it would “definitely be tens of thousands or millions.”

Heat waves already claim thousands of lives each year, and the study warns of more intense and frequent events in the decades ahead.

For instance, the 2023 southern Europe heat wave is now 70% more likely and 0.6°C warmer than it would have been before the Paris Agreement. Without stronger global action, a similar event at the end of the century could be 3°C hotter, the report said.

A heat wave like last year’s in the U.S. Southwest and Mexico could be 1.7°C warmer by 2100 under the current emissions trajectory.

Kristie Ebi, a public health and climate scientist at the University of Washington, said other studies have linked recent heat waves to hundreds of thousands of deaths — much of it directly tied to human-caused climate change.

Unequal burden of heat

The new study also exposes the deep inequality in how climate change impacts are distributed.

The 10 countries expected to face the biggest increase in superhot days — including the Solomon Islands, Samoa, Panama, and Indonesia — contribute barely 1% of the world’s carbon emissions but will endure nearly 13% of the extra heat days.

Panama, for example, is projected to face 149 more superhot days each year by 2100.

In contrast, top carbon-emitting nations like the United States, China, and India — responsible for 42% of atmospheric carbon dioxide — are expected to see only 23 to 30 extra superhot days.

“This report clearly shows what we’ve warned for decades,” said Andrew Weaver, a climate scientist at the University of Victoria. “Global warming is deepening inequality — punishing developing nations that contributed least to the problem, while driving new geopolitical tensions.”

Within the U.S., Hawaii and Florida are projected to see the largest increase in extreme heat days, while Idaho is expected to experience the smallest rise.

Still a dangerous path

While acknowledging that the Paris Agreement has slowed warming, Johan Rockström, director of the Potsdam Institute for Climate Impact Research, cautioned against complacency, reports UNB. 

“People should not feel relieved that we are no longer on the 4-degree trajectory,” he said. “The current path of 2.6 degrees still implies a disastrous future for billions of people on Earth.”