The global initiative to reduce emissions of greenhouse gases, which began a decade ago with the signing of the Paris climate agreement, has made notable progress. Researchers have determined that, without these efforts, the planet would be experiencing an additional 114 days each year of extreme heat, as highlighted in a recent study.

A collaboration between the international climate science group World Weather Attribution and the US-based organization Climate Central has employed computer simulations to evaluate the impact of this pivotal agreement. Their focus was on one of the most pressing climate challenges affecting humanity—heatwaves.

The findings, which are yet to undergo peer review but utilize established climate attribution methods, assess the number of exceptionally hot days the world endured in 2015, the current situation, and projections under two different future scenarios.

In one scenario, where countries adhere to their pledges to reduce emissions, it is projected that by 2100, the planet will warm by 2.6 degrees Celsius above preindustrial levels. This would result in an additional 57 extreme heat days compared to current figures, according to the study.

One scenario is if countries fulfill their promises to curb emissions and by the year 2100 the world warms 2.6 degrees Celsius above preindustrial times. That adds 57 superhot days to what Earth gets now, according to the study.

The other scenario is the 4C of warming that the world had been on track to hit before the Paris agreement. The study found that would double the number of additional hot days.

Pain and suffering coming

“There will be pain and suffering because of climate change,” said Climate Central Vice President for Science Kristina Dahl, a report co-author.

“But if you look at this difference between 4C of warming and 2.6C of warming, that reflects the last 10 years and the ambitions that people have put forth. And to me, that’s encouraging.”

Nearly 200 nations gather next month in Brazil for international climate negotiations. Numerous groups of scientists, analysts and advocates are compiling reports that show the same mixed bag: The 2015 Paris agreement has made strides in the fight against climate change but it’s too little and too slow.

Northern Illinois University climate scientist Victor Gensini said Thursday’s hot day findings “highlight both the success and shortfall of the Paris Agreement.”

The study defines superhot days for each location as days that are warmer than 90 per cent of the comparable dates between 1991 and 2020.

Since 2015, the world has already added 11 superhot days on average, the report said.

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

The report doesn’t say how many people will be affected by the additional dangerously hot days, but co-author Friederike Otto of Imperial College London said that “it will definitely be tens of thousands or millions, not less.” She noted that thousands die in heat waves each year already.

Imagine recent heat waves but worse

Thursday’s study calculated that the weeklong southern Europe heat wave in 2023 is now 70 per cent more likely and 0.6C warmer than it would have been 10 years ago when the Paris agreement was signed.

And if the world’s climate-fighting efforts don’t increase, a similar heat wave at the end of the century could be 3C hotter, the report estimated.

A heat wave similar to last year’s Southwestern United States and Mexico heat wave could be 1.7C hotter by the end of the century under the current carbon pollution trajectory, the report said.

Other groups are also finding more than hundreds of thousands of deaths from recent heat waves in peer-reviewed research with much of it because of human-caused climate change, said University of Washington public health and climate scientist Kristie Ebi, who wasn’t part of Thursday’s report.

More than anything, the data shows how unfair the effects of climate change seem, even under the less extreme of the two scenarios. The scientists broke down how many extra superhot days are expected for each country by the end of the century under that scenario.

Country data shows high heat inequality

The 10 countries that will see the biggest increases in those dangerous heat days are nearly all small and dependent on the ocean, including the Solomon Islands, Samoa, Panama and Indonesia. Panama, for example, can expect 149 extra superhot days.

Altogether the top 10 of those countries produced only 1 per cent of the heat-trapping gases now in the air but will get nearly 13 per cent of the additional superhot days.

But top carbon polluting countries, the United States, China and India are predicted to get only between 23 and 30 extra superhot days. They are responsible for 42 per cent of the carbon dioxide in the air, but are getting less than 1 per cent of the additional superhot days.

“This report beautifully and tangibly quantifies what we’ve been saying for decades. The impacts of global warming are going to disproportionally affect developing nations that historically haven’t emitted significant quantities of greenhouse gases,” said University of Victoria climate scientist Andrew Weaver, who wasn’t part of the study team.

“Global warming is driving yet another wedge between have and have not nations; this will ultimately sow seeds of further geopolitical instability.”

Hawaii and Florida are the US states that will see the biggest increase in superhot days by the end of the century under the current carbon pollution trajectory, while Idaho will see the smallest jump, the report found.

While the report makes sense, Potsdam Climate Institute Director Johan Rockstrom, who wasn’t part of the research, said people shouldn’t be relieved that we are no longer on the 4C warming pre-Paris trajectory because the current track “would still imply a disastrous future for billions of humans on Earth.”