As record-breaking heat waves sweep across nearly every continent amid accelerating global warming, air conditioning has emerged as a critical life-saving technology — but it also carries a steep environmental cost that deepens the climate crisis it helps people survive, leading climate and public health experts warn. A new peer-reviewed study published in *Nature Health* on Monday quantifies both the life-saving benefits and growing climate risks of widespread cooling use, offering a data-backed look at this urgent global dilemma.
Led by senior author Kai Chen, an epidemiology professor at the Yale School of Public Health, the research analyzed more than 30 million U.S. death records collected between 2010 and 2020, pairing county-level data on dangerous heat exposure with mortality outcomes to calculate air conditioning’s impact. The study found that cooling systems saved an average of 5,267 American lives each year over the 11-year period, with a total of nearly 58,000 lives saved across the decade. The largest number of lives saved were recorded in warm southern U.S. states including Arizona, Florida, Texas, Louisiana, Alabama and Mississippi, while northern states from Washington to Maine saw fewer than 10 lives saved annually due to less frequent extreme heat.
United Nations officials estimate that extreme heat kills roughly half a million people globally each year, and demand for cooling is skyrocketing as average global temperatures climb. Data from the U.S. Energy Information Administration shows the number of “cooling degree days” — a metric measuring how much energy is required to cool indoor spaces during hot weather — has risen 28% in the U.S. since 1990, with 2024 setting an all-time record and 2026 on pace to exceed that mark. Across Europe, cooling degree days have more than doubled since 1990, pushing air conditioning adoption up 44%. The trend is even starker in other major warm regions: cooling use has tripled in India and more than doubled across Southeast Asia, according to the International Energy Agency (IEA). The IEA and United Nations Environment Programme (UNEP) project global electricity demand from cooling will triple by mid-century.
This growing demand creates a dangerous feedback loop, experts explain: roughly 90% of the electricity powering today’s air conditioning systems comes from burning fossil fuels, which release heat-trapping greenhouse gases that warm the planet further. The UN projects that greenhouse gas emissions from air conditioning will jump from 4.5 billion metric tons annually to 7.2 billion metric tons over the next 25 years — an amount nearly equal to the total current carbon emissions of the United States and European Union combined.
“Everyone knows air conditioning works, but from a climate change perspective, it is not an ideal solution,” Chen explained. “It leads to more carbon emissions … then it accelerates the climate warming problem.” Beyond greenhouse gas emissions, cooling systems also amplify the urban heat island effect by expelling waste heat directly into outdoor city environments, and increased power demand worsens conventional soot and smog air pollution that harms public health.
Chen’s study also highlights widespread overuse of cooling in many developed regions, particularly in commercial buildings. Chen noted that many office spaces are cooled to such low temperatures that workers often wear sweaters even during the hottest summer months, and more than half of the cooling use examined in the study qualified as unnecessary overconsumption. The research confirms that excess cooling beyond a reasonable threshold does not save additional lives, but only increases carbon emissions and accelerates climate change. Chen recommends setting indoor cooling temperatures no lower than 75 degrees Fahrenheit (24 degrees Celsius) as a reasonable balance between comfort and sustainability.
A 2020s global energy crunch, exacerbated by geopolitical conflict, has already pushed multiple nations to implement cooling regulations to cut energy use and emissions. Eight countries including Bangladesh, Cambodia, Jordan, Malaysia, the Philippines, the Seychelles, Singapore and Sri Lanka have enforced maximum cooling limits for office air conditioning, and some have even mandated full cooling shutdowns one day per week in public buildings. India proposed similar national cooling limits in 2025.
The issue also carries profound equity implications, experts emphasize: many of the world’s most vulnerable low-income communities lack consistent access to affordable air conditioning, even as they face the worst impacts of rising heat. UNEP’s chief heat officer Eleni Myrivili notes that in recent extreme heat waves, many low-income families have been forced to choose between paying for life-saving medication and running their cooling systems. “In a warming world, thermal comfort should not be a luxury,” Myrivili said. “It’s becoming a prerequisite for health, dignity and increasingly survival.”
Global policymakers and experts from 75 countries and 250 cities are now working to navigate this tightrope: expanding access to life-saving cooling for vulnerable communities without worsening climate change. Delegates will gather in Singapore this September for the Global Cooling Pledge conference to coordinate collaborative action on sustainable cooling solutions.
Experts point to comprehensive policy approaches that combine passive cooling strategies and energy-efficient technology to cut emissions while expanding access. UNEP cooling unit head Lily Riahi highlighted Singapore as a leading model for integrated cooling action. The city-state has implemented a sweeping national strategy that combines passive cooling measures such as expanded urban greenery, which reduces ambient urban temperatures and cuts annual energy costs by an estimated $35 million, with mandatory energy-efficiency standards for cooling and ventilation systems in both new and existing buildings. The approach has lowered local outdoor temperatures by up to 8 degrees Celsius (14 degrees Fahrenheit) in some areas, Riahi said.
Riahi noted that passive, nature-based solutions are sufficient for many mild heat conditions, but extreme, humid heat events still require active air conditioning to protect public health. Experts emphasize the ultimate solution will require shifting cooling energy demand to renewable energy sources and rolling out highly efficient cooling technology to break the link between increased cooling access and rising carbon emissions. The goal, Riahi said, is not less cooling overall, but “smarter and more equitable cooling” that protects both human life and the global climate.