“Any further delays in climate change action will increasingly threaten the health and survival of billions of people alive today,” the report said. 

The study monitors the evolving impacts of climate change on health and the direct impact of climate action. It pointed to four main risk areas: rising temperatures that can put health at risk; extreme weather events that lead to food insecurity; the broader pressure on health care systems; and growing transmission of life-threatening diseases.

“Every heat-related death in my mind is avoidable,” said Dr. Renee Salas, an emergency medicine physician at Massachusetts General Hospital and Harvard Medical School who served as a senior author of the study. “And it is on us within the health sector to protect those people while simultaneously working upstream to get to the root cause and to transition away from fossil fuels.”

The report also details how some in the U.S. face particularly serious risks around heat.

Heat deaths are already climbing. The study found that heat-related deaths for U.S. adults aged 65 and older increased by 88% in 2018-2022 compared to 2000-04. This summer, Arizona’s Maricopa County shattered its record for heat deaths amid a brutal and lengthy heat wave.

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Infants were also far more likely to suffer during heat waves.

“The extremes of age are always a greater risk, and so infants under one year are just not able to tell us if they’re feeling too hot,” Salas said. 

The transmissibility of life-threatening viruses, like malaria, is also at risk of increasing. As  global temperatures rise, the likelihood of mosquitoes and ticks being able to survive and thrive in areas that they were not able to previously can also increase each year.

The report also points to near-term solutions for air pollution-related illnesses. Air pollution exacerbates many pre-existing conditions, like heart disease and asthma, in underserved communities.

“Nearly half of the deaths in the U.S. from air pollution are due to the burning of fossil fuels. And again, those lives can be saved,” Salas said. “These are near-term benefits that we can experience. And so it’s not abstract, or future oriented. It’s, in my mind, a health prescription that can be filled and seen.”