Global Warming Crisis: World Projected to Face 57 Additional Superhot Days Annually by 2100, Small Nations Most Vulnerable

The planet is projected to experience an additional 57 dangerously hot days annually by century's end, with smaller, economically disadvantaged nations facing disproportionate impacts compared to major carbon-emitting countries, according to research released Thursday.

Progress made through emissions reduction commitments following the Paris climate agreement has yielded significant benefits. Without these efforts, the world would be facing a far more severe scenario of 114 additional superhot days each year.

A collaborative study by World Weather Attribution and Climate Central utilized computer modeling to evaluate the Paris agreement's impact on one of climate change's most direct human threats: extreme heat events.

The report, using established climate attribution methodologies though not yet peer-reviewed, analyzed superhot day patterns across more than 200 countries in 2015, present day, and under two future projections.

In one scenario, where nations fulfill their emissions reduction commitments resulting in 2.6 Celsius warming above pre-industrial levels by 2100, the world would experience 57 additional superhot days annually beyond current levels. The alternative scenario—a 4 Celsius warming trajectory that existed before the Paris agreement—would double this increase.

"Climate change will inevitably cause suffering," explained Climate Central's Vice President for Science Kristina Dahl, who co-authored the report. "However, comparing the 4 degrees scenario against the 2.6 degrees projection demonstrates the meaningful impact of the past decade's climate commitments, which offers some encouragement."

The study defines superhot days as those exceeding the temperature of 90% of comparable dates between 1991-2020. Since 2015, the world has already gained an average of 11 superhot days annually.

"These extreme heat conditions lead to emergency hospitalizations and fatalities," Dahl noted.

While the report doesn't quantify exact population impacts from these additional heat days, co-author Friederike Otto from Imperial College London estimates "tens of thousands or millions" will be affected, noting that heat waves already cause thousands of deaths annually.

The researchers calculated that the 2023 southern European heat wave is now 70% more likely and 0.6 Celsius warmer than it would have been before the Paris agreement. Without enhanced climate action, similar future heat waves could be 3 Celsius hotter by 2100.

Heat waves resembling last year's event in the Southwestern United States and Mexico could be 1.7 Celsius hotter by century's end under current emission trajectories.

Independent peer-reviewed research has confirmed hundreds of thousands of deaths from recent heat waves, largely attributable to human-induced climate change, according to University of Washington scientist Kristie Ebi, who wasn't involved in Thursday's study.

The data reveals stark climate inequity even under the more moderate warming scenario. The study detailed expected additional superhot days for each country by 2100.

The ten nations facing the most severe increases are predominantly small, ocean-dependent countries like the Solomon Islands, Samoa, Panama, and Indonesia. Panama alone is projected to experience 149 additional superhot days. Collectively, these ten most-affected countries have contributed only 1% of atmospheric greenhouse gases but will endure nearly 13% of the additional extreme heat days.

Meanwhile, the leading carbon polluters—the United States, China, and India—are projected to experience just 23-30 additional superhot days. Despite being responsible for 42% of atmospheric carbon dioxide, they will face less than 1% of the additional extreme heat burden.

"This report effectively quantifies what we've understood for decades—global warming's impacts will disproportionately affect developing nations with historically minimal greenhouse gas emissions," said climate scientist Andrew Weaver from the University of Victoria, who wasn't involved in the study. "Global warming is expanding inequality between advantaged and disadvantaged nations, potentially fueling further geopolitical instability."

Within the United States, Hawaii and Florida will experience the largest increases in superhot days by 2100 under current emission trajectories, while Idaho will see the smallest increase.

While the findings demonstrate improvement from pre-Paris scenarios, Potsdam Climate Institute Director Johan Rockstrom, who wasn't part of the research team, cautioned against complacency, noting that the current warming trajectory "would still create catastrophic conditions for billions of people worldwide."