LONDON, July 23 (Thomson Reuters Foundation) - A hotter planet could lead to tens of thousands more suicides by 2050 in the United States and Mexico alone, unless global warming is curbed, according to a study published on Monday.
Researchers examined decades worth of temperature data against suicide rates in U.S. counties and Mexican municipalities, some dating back to the 1960s, and found that hotter weather was linked to increases in deaths by suicide.
"Hotter temperatures are clearly not the only, nor the most important, risk factor for suicide," lead author Marshall Burke, an economist at Stanford University, said in a statement.
"But our findings suggest that warming can have a surprisingly large impact on suicide risk, and this matters for both our understanding of mental health as well as for what we should expect as temperatures continue to warm," he said.
According to their analysis, a 1 degree Celsius (1.8 degrees Fahrenheit) increase in average monthly temperature led to a 0.7 percent rise in suicide rates in the United States, and a 2.1 percent rise in Mexico.
The paper, published in the journal Nature Climate Change, also analyzed the language used in over half a billion Twitter posts and found that suicide rates and depressive language increased during hot weather.
The study projected that if global warming is not capped by 2050, there could be at least an additional 21,000 suicides in the two countries alone.
See severe summer weather in the U.S. so far in 2018:
Summer weather across the US in 2018
Summer weather across the US in 2018
NEWPORT BEACH, CA - AUGUST 17: A man and his nephew enjoy the warm water at Salt Creek Beach in Dana Point on Friday, August 17, 2018. (Photo by Paul Bersebach/Orange County Register via Getty Images)
NEW YORK, NY - AUGUST 17: People cool themselves during a warm day at Central Park on August 17, 2018 in New York City. Severe thunderstorms and even an isolated tornado could strike New York City on Friday. (Photo by Eduardo Munoz Alvarez/Getty Images)
WEEHAWKEN, NJ - AUGUST 17: A man takes a look of the haze over the New York skyline and One World Trade Center on August 17, 2018 in Weehawken, New Jersey. Severe thunderstorms and even an isolated tornado could strike New York City on Friday. (Photo by Eduardo Munoz Alvarez/Getty Images
NEWPORT BEACH, CA - AUGUST 10: A surfer loses it on a wave in Newport Beach on Friday, August 10, 2018. A swell from Hurricane John will bring larger waves to south-facing beaches through the weekend. (Photo by Paul Bersebach/Orange County Register via Getty Images)
A man sunbathes on Venice Beach in Los Angeles, California on August 7, 2018. Temperatures climbed to near 100 degrees as a week-long heat wave continues in Southern California. (Photo by Ronen Tivony/NurPhoto via Getty Images)
WELLFLEET, MA - JUNE 21: Mark Wilke and his wife Sharon enjoy the first day of summer at White Crest Beach in Wellfleet, MA on June 21, 2018. (Photo by Craig F. Walker/The Boston Globe via Getty Images)
ARLINGTON, VA - JUNE 20: A pedestrian passes near the Netherlands Carillon as the Washington Monument and United States Capitol are seen at sunrise on Wednesday June 20, 2018 in Arlington, VA. The summer solstice is Thursday. (Photo by Matt McClain/The Washington Post via Getty Images)
Pedestrians watch sailboats and windsurfers on the Charles River on the summer solstice in Boston, Massachusetts, U.S., June 21, 2018. REUTERS/Brian Snyder
A women keeps in the shade of her umbrella as she tries to beat the heat at Cardiff State beach in Encinitas, California, U.S. July 6, 2018. REUTERS/Mike Blake
A man cools off in fountain on the Rose Kennedy Greenway during a summer heat wave in Boston, Massachusetts, U.S., July 2, 2018. REUTERS/Brian Snyder
OLD ORCHARD BEACH, ME - JULY 4: Ryan Parsons, left, of Unity watches as his daughter, Lily, 10, rides the waves on her inflatable whale at Old Orchard Beach on a hot, beautiful Fourth of July. The Parson family was spending the day at the beach keeping cool and watching the fireworks. (Staff photo by Jill Brady/Portland Press Herald via Getty Images)
NEW JERSEY, USA - JUNE 30: People enjoy Manhattan skyline at the Hamilton Park during the hot weather in New Jersey, United States on June 30, 2018. (Photo by Atilgan Ozdil/Anadolu Agency/Getty Images)
NEW YORK, July 2, 2018 -- People cool themselves at a fountain at Washington Square Park in New York City, the United States, on July 2, 2018. The highest temperature reached 35 degrees Celsius in New York City on Monday as a result of a prolonged heat wave. (Xinhua/Wang Ying via Getty Images)
NEW YORK, USA - JULY 23: Rain clouds are seen over Lower Manhattan in New York, United States on July 23, 2018. (Photo by Atilgan Ozdil/Anadolu Agency/Getty Images)
NEW JERSEY, USA - JULY 27: People walk with their umbrellas during a rainy day at the Liberty State Park in New Jersey, United States on July 27, 2018. (Photo by Atlgan Ozdil/Anadolu Agency/Getty Images)
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Suicide rates rose in nearly every U.S. state from 1999 to 2016, with the rate spiking by more than 30 percent in half of the country, the Centers for Disease Control and Prevention reported in June.
Nearly 45,000 people committed suicide in 2016, making it one of three leading causes of death on the rise in the United States, along with Alzheimer's disease and drug overdoses.
"When talking about climate change, it's often easy to think in abstractions," said Burke, an assistant professor in environmental sciences.
"But the thousands of additional suicides that are likely to occur as a result of unmitigated climate change are not just a number, they represent tragic losses for families across the country," he said.
The past three years were the hottest on record, the United Nations' World Meteorological Organisation said in March.
The World Health Organization says that heat stress, linked to climate change, is likely to cause 38,000 extra deaths a year worldwide between 2030 and 2050.
In a heat wave in May, more than 60 people died in Karachi, Pakistan, when the temperature rose above 40C (104F).
In 2015, countries signing the Paris Agreement set a goal of limiting a rise in average world surface temperatures to "well below" 2C (3.6F) above pre-industrial times, while "pursuing efforts" to limit rising temperatures to 1.5C (2.7F).
U.S. President Donald Trump has vowed to pull out of the accord, which would make his country the only one to do so.
(Reporting by Lin Taylor @linnytayls, Editing by Jared Ferrie; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters that covers humanitarian issues, conflicts, land and property rights, modern slavery and human trafficking, gender equality, climate change and resilience. Visit http://news.trust.org to see more stories)