"But heat is also affecting not just the mortality and increasing deaths, but also increasing the diseases and the pathologies associated with heat exposure," she said.
For example, people who exercise outdoors are increasingly at risk, she said. Companies are facing limited capacity for working outdoors.
In fact, last year's extreme heat cost the world an estimated 512 billion potential labor hours, worth hundreds of billions of dollars in potential income, the report said.
"Similar to what we saw with the COVID-19 pandemic, it is key workers who tend to be most exposed and unable to shield as easily during heatwaves, such as those working in one of our many hospitals without air conditioning, or outdoor construction workers," said data scientist Nathan Cheetham at King's College London in a statement. Cheetham was not involved in the study.
Climate change is also making food more unreliable, the authors warned.
With up to 48% of the world's land area facing extreme drought conditions last year, the researchers said, about 151 million more people would be experiencing food insecurity as a result, compared with the years 1981-2010.
Extreme rainfall last year also affected roughly 60% of lands, unleashing floods and raising risks from water contamination or infectious disease.
The study's authors urged the upcoming U.N. climate summit, COP29, to direct climate finance toward public health. The COP29 talks begin Nov. 11 in Baku, Azerbaijan.
U.N. Secretary-General Antonio Guterres on Tuesday called on countries to "cure the sickness of climate inaction" by slashing fossil fuel use and emissions in order "to create a fairer, safer, and healthier future for all."
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