Researchers with the Lancet Countdown found that human-caused warming accounted for more than 70% of a record 710,000 heat-related deaths worldwide in 2023.
They now insist on an official global health emergency designation for climate change.
Here's what to know
Led jointly by University College London and the World Health Organization, the research assessed 54 indicators of how a changing climate affects global human health, The Independent reported.
The Lancet Countdown project brought together more than 140 specialists from over 30 nations.
Researchers found that the annual global average of deaths attributable to heat has risen nearly 36% since the Paris Agreement was adopted in 2015.
"A decade after the Paris Agreement, our findings are unambiguous: the health harms of climate change are growing faster than the world's response to them, and in many cases even accelerating," Lancet Countdown executive director Professor Marina Romanello explained.
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The Lancet Countdown also found that climate-related health dangers intensified more rapidly in the decade after the agreement than in the decade before it.
The assessment considers communities' exposure to health threats alongside the systems intended to protect them.
Researchers examined legislation, research funding, health adaptation, and energy infrastructure, as well as economic damage, extreme weather, disease spread, and air pollution.
More background
Satellite analyses cited in the report also revealed substantial changes in groundwater storage, both wetter and drier, across 80% of Earth's land since 2003.
According to the Lancet Countdown, almost 52% of the world's land experienced severe drought during at least one month of 2025, the second-largest on record.
Sanitation and food security are also at risk.
Meanwhile, fossil fuels still supply more than 80% of the world's energy, the findings show.
Researchers calculated that the 100 biggest oil and gas producers are on course to exceed production levels compatible with the global community's widely agreed-upon goal of limiting warming to 2.7 degrees Fahrenheit (1.5 degrees Celsius) by 150% in 2040.
What's being done?
There have been some positive changes. Lower air pollution averted approximately 323,000 deaths a year in 77 countries where fossil fuel emissions declined after 2016.
Clean energy investment reached a record in 2025, nearly twice that of fossil fuel investment.
Romanello emphasized the benefits of advances in clean energy, health system preparedness, and health-protecting regulations.
To acknowledge the scale of the danger, the report's authors proposed officially designating climate change a global health emergency. They also called for decisions on emissions cuts and funding allocation to prioritize human health impacts.
"Real progress has been made in clean energy, health system readiness, and health-protective regulation, all of which are already delivering health benefits to local communities. However, progress has been too slow, too small, and isn't reaching those who need it most," said Romanello.
"That is why we are calling for climate change to be formally recognized as a global health emergency, with health placed at the center of every climate decision," she concluded.
Where can I learn more?
As heat deaths rise worldwide, keeping people safe in extreme temperatures is increasingly urgent. These stories explore deadly heat in Europe, projected deaths in the Global South, and the life-saving role of air conditioning.
• Western Europe's record heat killed at least 35,000 people, drawing a stark WHO warning.
• El Niño could cause 451,000 extra heat deaths, concentrated in the Global South.
• Air conditioning cuts U.S. heat deaths in half, but extreme temperatures still increase risks.
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