When I started reporting on the ways climate change is affecting human health, sources repeatedly told me the same thing: no one actually knows the scale of the problem. Official estimates vastly undercount lives lost to heat, wildfire smoke and flooding, making climate’s toll easy to ignore.
That leads to an obvious question. How many people is climate change hurting and killing?
I was a climate scientist before I came back to journalism, so a question like this is catnip to me. My instinct was to try to answer it with rigorous, careful science — and, of course, report from the ground, learning from the people who were living through the consequences.
So that’s what we did. Alongside research scientists from Boston University, we spent two years developing a model that estimates how many deaths across the U.S. are influenced by heat each year. Our exclusive analysis found a staggering hidden toll: Heat kills nearly 5 times more people than official numbers show.
Then, I went into the field to ground-truth our findings and to learn why so many people were dying — and how their deaths could go uncounted. I spent time with people in their stiflingly hot mobile homes in Arizona; finding pockets of shade to rest in with unhoused people in California; and talking with outdoor workers in Washington state.
Now, we’re sharing that reporting with you. In today’s story, we have included maps that let you search for your county and state to see how many lives heat has taken near the place you live.
Heat isn’t just uncomfortable. As our investigation shows, it can kill. Yet, as Quinn Adams, our collaborator from Boston University, says, it’s all too easy to discount.
“Most people do not see themselves as vulnerable to heat. They're like, Oh, that's someone else. It's not me,” she says. But when it’s not taken seriously, suddenly, “it actually is you.” Please stay safe this summer and all those to come. | 
