This is roughly the same change in suicide rates as are driven by “the estimated impact of economic recessions, suicide-prevention programs, or gun-restriction laws.”

It also concludes that humans can do little about this suicide-climate link beyond developing better medical care to address suicide specifically. The normal ways that people adapt to high temperatures generally—by installing air conditioners, for instance—do not seem to affect the suicide rate.

Suicide is the second most-common cause of death among Americans between 10 and 34 years of age. It is also one of the few leading causes of death in the United States where the age-adjusted mortality rate is not falling. In other words, more people are dying by suicide than used to.

“I found the results compelling and the methodology strong,” says Gregory Tasian, a professor of epidemiology and biostatistics at the University of Pennsylvania who was not related to the study.

“It fits very well into the overall narrative about the effect of climate change and high temperatures on human health—and it incorporates another aspect of human health which is often neglected, which is mental health,” he told me.

The new paper provides unusually robust evidence that high temperatures will significantly aggravate the problem of suicide.

First, the new paper makes a causative claim: Unusually high temperatures really do seem to cause suicide rates to increase. The authors have controlled for every other major variable that might affect suicide rates. The effect doesn’t seem to change if the victims are men or women, if the month is January or June, if they live in an American city or the Mexican countryside. Nor does it vary in areas where guns are plentiful.

Second, it finds that the effect shows up everywhere: in Saint Paul and San Antonio, in Ohio and Oaxaca. “We see the exact same effect size in hot places versus cold places,” Burke told me.

Previous studies of climate change and mortality have found that global warming’s effects on mortality will be mixed. In a landmark study last year, for instance, a team of economists found that warmer temperatures will grant modest economic benefits to the upper Midwest and New England, since they will blunt those regions’ deadly winters. (The Sunbelt will suffer far worse costs during the summer, however.)

Not so for the suicide rate, which will increase ubiquitously under global warming.

“‘Climate change is going to generate winners and losers’—this is a phrase you hear all the time,” Burke said. “But for this outcome, it’s all losers. There are no winners. We find these strong linear relationships everywhere when you crank up the temperature.”

Finally, the paper finds there are few ways to blunt this effect. In previous studies, economists have found that air-conditioning adoption causes heat-related mortality to decrease over time. But the climate-suicide link does not show the same pliability.