Health Risks Due to Climate Change Are Rising Dangerously, Lancet Report Concludes

An international monitoring project established at the time of the Paris Agreement reported Wednesday that climate-related risks to health are worsening, with more people facing dangerous heat, food insecurity, exposure to pathogens and other threats.

The team of 122 researchers from United Nations agencies and academic institutions worldwide published their findings in The Lancet in advance of climate negotiations scheduled for next month in Azerbaijan. The findings were accompanied by an urgent plea from the authors for stronger action by governments to protect lives.

“This year’s stocktake of the imminent health threats of climate inaction reveals the most concerning findings yet in our eight years of monitoring,” Marina Romanello, executive director of the Lancet Countdown project at University College London, said in a statement. “The relentless expansion of fossil fuels and record-breaking greenhouse gas emissions compounds these dangerous health impacts, and is threatening to reverse the limited progress made so far, and put a healthy future further out of reach.”

The Lancet Countdown project, which has been tracking a set of more than 40 climate health risk indicators since 2016, added several new factors to its assessment this year. For the first time, the team included measures of increased exposure to extreme precipitation and to desert dust, highlighting the wide range of impacts caused by the increasing concentration of greenhouse gases in the atmosphere. They also looked at the effect of rising night-time temperatures on sleep loss as part of their tracking of how climate change can affect mental health and well-being.

Many of the risk indicators were driven higher because 2023 was the hottest year on record. The scientists used temperature and other weather data, population estimates and epidemiological risk modeling to come up with their results. Some of the team’s most dramatic health findings:

• Heat-related mortality of people older than 65 increased 167 percent compared with the 1990s. Such deaths would have risen in any case because the aging population is larger, but the researchers concluded the increase is 102 percentage points higher than it would have been with no temperature rise.

• In 2023, people were exposed, on average, to 1,512 hours during which ambient heat posed at least a moderate risk of heat stress during light outdoor exercise—328 hours, or about 28 percent more than the 1990-1999 annual average. 

• Heat exposure led to 512 billion potential work hours lost in 2023, 49 percent above the 1990-1999 average. Sixty-three percent of those potential lost work hours occurred in the agricultural sector.

• Sleep hours lost due to high temperatures increased by 5 percent between 1986-2005 and 2019–2023. The researchers controlled for demographic and environmental factors, including access to air conditioning. “Sleep of adequate duration and quality is important for good human physical and mental health,” the authors wrote.

• Climate conditions favorable for transmission of illness from the Asian tiger mosquito (Aedes albopictus) increased about 46 percent from 1951-1960 to 2014-2023. For the so-called “yellow fever mosquito” (Aedes aegypti), the increase was more than 10 percent. The mosquitos are associated with dengue, chikungunya, Zika virus and other diseases. A separate study recently found that 2023 was the worst year ever recorded for dengue globally, with 6.5 million cases and more than 6,800 deaths reported.

• Sixty-one percent of the global land area saw an increase in the number of days of extreme precipitation from 1961-1990 to 2014-2023. This, in turn, increases the risk of flooding, infectious disease spread and water contamination, the researchers said.

• Some 3.8 billion people were exposed to mean annual concentrations of small particulate pollution from sand and desert dust that exceeded World Health Organization guideline levels from 2018 to 2022. That’s a 31 percent increase in risk since 2003-2007. The researchers said drought, poor land management and increased wildfire-burned areas are increasing the risk.

• The higher frequency of heatwave days and drought months in 2022, compared with 1981-2010, was associated with 151 million more people experiencing moderate or severe food insecurity across 124 countries in 2022, compared with 1981-2010.

“This year’s report reveals a world veering away from the goal of limiting temperature rise to 1.5°C,” the authors wrote. “People all around the world are facing record-breaking threats to their wellbeing, health and survival from the rapidly changing climate.”

The researchers did point to one positive climate-related health development in the past decade. Deaths attributable to outdoor fine particulate pollution from fossil fuel combustion decreased about 7 percent between 2016 and 2021. The authors attributed this to the phase-out of coal electricity in high-income countries like the United States, and noted the “life-saving potential” of such measures.

“Putting health at the center of climate action represents the biggest opportunity of our lives to secure a thriving future for all,” Helen Clark, the former New Zealand prime minister who chairs the independent board that oversees the Lancet Countdown project, said in a statement. “This report is a clarion call to act now to protect ourselves, each other, and future generations.”