San Francisco at noon on September 9, 2020, as wildfire smoke blanketed the Bay Area.Santiago Mejia/San Francisco Chronicle via Getty/Grist

This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

Wildfire smoke is an emerging nationwide crisis for the United States. Supercharged by climate change, blazes are swelling into monsters that consume vast landscapes and entire towns. A growing body of evidence reveals that these conflagrations are killing far more people than previously known, as smoke travels hundreds or even thousands of miles, aggravating conditions like asthma and heart disease. One study, for instance, estimated that last January’s infernos in Los Angeles didn’t kill 30 people, as the official tally reckons, but 440 or more once you factor in the smoke. Another recent study estimated that wildfire haze already kills 40,000 Americans a year, which could increase to 71,000 by 2050.

Two additional studies published last month paint an even grimmer picture of the crisis in the US and elsewhere. The first finds that emissions of greenhouse gases and airborne particles from wildfires globally may be 70 percent higher than once believed. The second finds that Canada’s wildfires in 2023 significantly worsened childhood asthma across the border in Vermont. Taken together, they illustrate the desperate need to protect public health from the growing threat of wildfire smoke, like better monitoring of air quality with networks of sensors.

The emissions study isn’t an indictment of previous estimates, but a revision of them based on new data. Satellites have spied on wildfires for........

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