**A Decade After Paris Agreement: Progress Is Slow But Still Crucial in Curtailing Extreme Heat**
Ten years have passed since the landmark Paris climate agreement was adopted in 2015, aiming to limit global warming to well below 2 degrees Celsius above preindustrial levels, and ideally to keep it under 1.5 degrees Celsius. Despite widespread international commitment, progress in curbing global warming has been uneven and modest at best. However, new research indicates that even this limited progress is making a meaningful difference in reducing the severity of future extreme heat events, which are becoming an increasing threat worldwide.
This insight is particularly relevant as delegates from nearly 200 countries gather at COP30, the United Nations Climate Change Conference held in Brazil in 2025. The conference focuses on implementing and advancing commitments under the Paris Agreement. Scientists, environmental advocates, and vulnerable nations are emphasizing the importance of pushing forward with climate action—even if it is imperfect—because of the tangible benefits it yields in mitigating extreme heat and its deadly consequences.
### The Escalating Threat of Extreme Heat
Global warming has unequivocally intensified heat waves across the planet, making them more frequent, longer-lasting, and more severe. Heat waves now rank as the deadliest form of weather-related hazard, with their toll accelerating sharply. In the United States alone, deaths attributed to extreme heat have surged by 53% over the last decade, compared to a 7% increase in deaths related to cold weather, according to a recent study published in *JAMA Network Open*. Globally, heat-related mortality has climbed by 63% since the 1990s, according to the 2025 report from the Lancet Countdown on Health and Climate Change.
These trends underscore the urgency of limiting further temperature increases. When the Paris Agreement was finalized in 2015, the global average temperature had already risen approximately 1 degree Celsius above preindustrial levels—a benchmark defined as the late 19th century period before extensive fossil fuel use began heating the planet. The Paris Agreement’s goal was to hold temperature increases well below 2 degrees Celsius and to pursue efforts to keep warming under 1.5 degrees Celsius.
### Current Warming and Its Impact on Extreme Heat
As of 2024, the global average temperature has already surpassed the 1.5-degree Celsius threshold in some measurements, with a long-term warming signal currently estimated at around 1.3 degrees Celsius above preindustrial levels. While a 0.3-degree increase since 2015 may seem minor, its real-world impact is profound. Research by Climate Central and World Weather Attribution shows that this rise has resulted in an average of 11 additional extremely hot days per year globally—defined as the hottest 10% of days in any country. For some nations, the increase is even more pronounced, intensifying the health risks and strain on infrastructure.
Despite this, the progress made since the Paris Agreement is significant when viewed against the alternative scenarios. Prior to the agreement, projections indicated the world was on track for a staggering 4 degrees Celsius of warming. That level would have led to an average of 114 more extremely hot days globally each year, with some countries like Indonesia potentially experiencing over 300 additional extremely hot days annually. Thanks to current efforts, forecasts now place the world’s trajectory between 2.5 and 3 degrees Celsius of warming, effectively halving the number of additional extremely hot days expected.
Climate scientist Friederike Otto from Imperial College London, a co-author of the recent joint study, emphasized the critical difference even small fractions of a degree make: “Every fraction of a degree of warming—whether it is 1.4, 1.5, or 1.7°C—will mean the difference between safety and suffering for millions of people.”
### The Risks of Heat Waves Under Different Warming Scenarios
The study also examined the severity and likelihood of recent devastating heat waves that have caused tens of thousands of deaths and triggered widespread droughts and wildfires. Under a 4-degree Celsius warming scenario, such heat waves would be 3 to 6 degrees Celsius hotter than current events and would be 5 to 75 times more likely to occur. In contrast, limiting warming to around 2.6 degrees Celsius would still make these events 1.5 to 3 degrees Celsius hotter and 3 to 35 times more likely, but the risks and impacts would be considerably lower.
This stark contrast highlights how crucial