More disease, more suicide: Study shows human cost of climate change

Climate change is not only warming the planet, it's negatively affecting human health in myriad ways, with researchers reporting surges in heat-related illnesses, infectious diseases, poor sleep and an increase in suicides, according to a major report by The Lancet Countdown that's been cosigned by health experts from more than 70 institutions worldwide.

"There is no safe temperature rise from a health standpoint," Dr. Renee Salas, an author of the report and an assistant professor of emergency medicine at Harvard, said at a press briefing on Tuesday. "The take-home message of this year's brief is clear: Climate change is first and foremost a health crisis."

Additionally, the report shows how decades of racial inequity has deepened divides when it comes to health outcomes, especially in the U.S. over the last few decades, as researchers have observed an increase in the intensity, duration and frequency of heat waves, wildfires and droughts.

More than a third of urban heat-related deaths in the 1990s and early 2000s can be attributed to climate change, and extensive research also has shown that exposure to heat waves poses a range of health risks, from heat rashes to heat exhaustion to heatstroke.

"During the last heat wave, I saw paramedics with burns on their knees from kneeling down on the sidewalk to take care of patients with heatstrokes," said Dr. Jeremy Hess, a co-author of the report and a professor of environmental and occupational health services at the University of Washington. "I have seen patients die of heatstroke this year. These are preventable problems."

Warmer temperatures also contribute to people sleeping less and observable increases in suicide and crime.

"Patients tend to complain more about sleep disturbances during heat waves, which generally go away once the weather passes," said Dr. Shehram Majid, a New York City-based psychiatrist. "I have seen a rise in patients struggling with mood and anxiety disorders during periods of extreme weather in NYC."

One study estimates that in the U.S., suicide rates rise 0.7% for every 1 degree Celsius increase in average temperature.

Climate change also creates and exacerbates droughts, which can lead to more wildfires that burn for much longer, which means more dust and smoke that destroys air quality. Agriculture suffers. Pollen levels can increase, affecting those with allergies.

And poor air quality can be felt thousands of miles away from fires. In July 2021, smoke from California's Dixie Fire reached the Eastern Seaboard, contributing to the worst air quality in New York City in 15 years.

"September 2020, we saw the max wildfires to date, with about 80,000 wildfires in the U.S., which is eight times greater than 2001," Salas added.

Emerging evidence, cited in the report, also shows that wildfire smoke may be more harmful than many other types of smoke, especially for children. Exposure has been linked to an increased risk of heart and pulmonary disease, premature death, worsened mental health and greater risk of preterm birth.

More flooding can create conditions that lead to increased mosquito breeding, which means diseases such as Dengue fever, a dangerous viral infection, can spreader wider more quickly via the insects.

"New Dengue transmission potential is five times higher than 1950," Salas added.

Longer warm seasons also means more ticks are spreading Lyme disease.

"We spent many years talking about the pandemic, yet we were not prepared. We are bound to make the same mistake again with climate change. We have not invested in the mitigation and adaptation necessary," said Dr. Georges Benjamin, executive director of the American Public Health Association. "The health sector is already stressed, and when you add these natural disasters it pushes things to the breaking point."

Policymakers need to get serious about taxing carbon and reaching zero-emission targets, said Benjamin, adding: "This is an opportunity to invest differently in a green recovery that isn't fueled by fossil fuels. We could be investing in a healthier future. This is a pivotal moment in history."

Yalda Safai, M.D., M.P.H., a psychiatry resident in New York City, is a contributor to ABC News Medical Unit.