Climate change continues to have a worsening effect on health and mortality around the world, according to an exhaustive report published on Tuesday by an international team of 114 researchers.
One of the starkest findings is that heat-related deaths of people older than 65 have increased by 85 percent since the 1990s, according to modeling that incorporates both changing temperatures and demographics. People in this age group, along with babies, are especially vulnerable to health risks like heat stroke. As global temperatures have risen, older people and infants now are exposed to twice the number of heat-wave days annually as they were from 1986 to 2005.
The report, published in the medical journal The Lancet, also tracked estimated lost income and food insecurity. Globally, exposure to extreme heat, and resulting losses in productivity or inability to work, may have led to income losses as high as $863 billion in 2022. And, in 2021, an estimated 127 million more people experienced moderate or severe food insecurity linked to heat waves and droughts, compared with 1981-2010.
“We’ve lost very precious years of climate action and that has come at an enormous health cost,” said Marina Romanello, a researcher at University College London and the executive director of the report, known as The Lancet Countdown. “The loss of life, the impact that people experience, is irreversible.”
The indicators of public health tracked in the report have generally declined over the nine years the researchers have produced editions of the assessment.
The analysis also examined health outcomes for individual countries, including the United States. Heat-related deaths of adults 65 and older increased by 88 percent between 2018 and 2022, compared with 2000-04. An estimated 23,200 older Americans died in 2022 because of exposure to extreme heat.
For health practitioners, the statistics are not abstract or faceless.
“These numbers remind me of the elderly patients I see in my own hospital with heatstroke,” said Dr. Renee Salas, an emergency medicine physician at Massachusetts General Hospital and Harvard Medical School.
Dr. Salas is one of the report’s co-authors and said she viewed the project like tracking vital signs in a patient, but on a national and international scale.
The data can help fill a gap for federal policymakers.
“We have a limited set of indicators for climate change and health that are routinely collected in the United States,” said Dr. John Balbus, director of the office of climate change and health equity in the U.S. Department of Health and Human Services. He did not contribute to this report and is not currently involved with The Lancet Countdown, but previously served as a scientific adviser to the project’s funder.
Dr. Balbus cautioned that this report mostly measures people’s exposure to climate-related risks rather than actual health outcomes, such as rates of disease. In order to get from exposures to real health outcomes, he said more investment in research was needed.
For the first time, this year’s Lancet Countdown included projections for the future. If the global average temperature rises by 2 degrees Celsius compared with pre-industrial temperatures, an increasingly likely future unless society significantly reduces greenhouse gas emissions, the number of heat-related deaths each year will increase by 370 percent by the middle of this century, the report found.
At the same time, the researchers point out that reducing fossil fuel pollution is proving beneficial for global health. Deaths from air pollution related to fossil fuels have decreased by 15 percent since 2005, with most of that improvement a result of less coal-related pollution entering the atmosphere.
The value of The Lancet Countdown is its ongoing monitoring of climate change’s effects on global health, said Sharon Friel, director of the Planetary Health Equity Hothouse at the Australian National University.
Dr. Friel was not involved in the report, but read it and wrote an accompanying commentary.
Dr. Howard Frumkin, a former special assistant to the director for climate change and health at the Centers for Disease Control and Prevention, said the report was a valuable dashboard but that the climate impacts he most worried about were not the obvious ones highlighted. Researchers and policymakers need to pay attention to the health effects of people being displaced by climate change and migrating, Dr. Frumkin said.
“If you’re on cancer chemotherapy or if you are getting kidney dialysis or if you’re getting addiction treatment and you have to move suddenly, that’s terribly disruptive and threatening,” he said. Dr. Frumkin was not involved in the new report but was a co-author on previous editions.
Over the years, the health experts involved in this project have included more research about the continued use of fossil fuels being the root cause of health issues.
“The diagnosis in this report is very clear,” Dr. Salas said. “Further expansion of fossil fuels is reckless and the data clearly shows that it threatens the health and well-being of every person.”
The researchers point out that health care systems, and other societal infrastructure health care depends on, haven’t adapted quickly enough to our current level of global warming.
“If we haven’t been able to cope today, chances are we won’t be able to cope in the future,” Dr. Romanello said.
The report is likely to be discussed at the annual United Nations climate summit in the United Arab Emirates that starts in a few weeks. This year the summit will include a greater focus on human health.