WASHINGTON (AP) — A recent study suggests that the world is on a trajectory to experience nearly two additional months of perilously hot days annually by the century’s end, disproportionately affecting smaller, less affluent nations compared to the major carbon-emitting countries.

However, actions to reduce greenhouse gas emissions, initiated a decade ago with the Paris climate accord, have made a notable difference. Without these efforts, Earth would be facing an extra 114 days of dangerously high temperatures each year, the study concluded.

The study was a collaborative effort between World Weather Attribution, a group of international climate experts, and the U.S.-based organization Climate Central. They employed computer models to assess the impact of the historic agreement on one of the most significant climate-related threats to humanity: heat waves.

The findings, while not yet peer-reviewed, utilized reputable climate attribution techniques to estimate the increase in superhot days globally and in over 200 countries from 2015 to the present, as well as projecting two future scenarios.

In one scenario, if nations meet their emission reduction commitments, the world would warm by 2.6 degrees Celsius (4.7 degrees Fahrenheit) above preindustrial levels by 2100, adding 57 superhot days compared to now. The other scenario considers a 4-degree Celsius (7.2 degrees Fahrenheit) rise, which was the pre-Paris agreement trajectory, potentially doubling the number of extra hot days.

Pain and suffering coming

Kristina Dahl, Vice President for Science at Climate Central and a co-author of the report, remarked, “Climate change will inevitably bring challenges and hardships. Yet, the contrast between a 4-degree and a 2.6-degree Celsius increase reflects the progress and determination over the last decade, which I find hopeful.”

The study defines superhot days for each location as days that are warmer than 90% 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% more likely and 0.6 C (1.1 F) 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 3 C (5.4 F) hotter, the report estimated.

A heat wave similar to last year’s Southwestern United States and Mexico heat wave could be 1.7 degrees Celsius (3.1 degrees Fahrenheit) 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% of the heat-trapping gases now in the air but will get nearly 13% 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% of the carbon dioxide in the air, but are getting less than 1% 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 U.S. 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 4-degree warming pre-Paris trajectory because the current track “would still imply a disastrous future for billions of humans on Earth.”