This is the worst fire season the American West has ever seen

ON SEPTEMBER 9TH residents of California, Oregon and Washington state woke up to a disturbing sight: an orange-tinted sky filled with smoke from nearby wildfires. Some reported ash falling from the sky like snow; others struggled to capture the eerie sight accurately because the software on their mobile phones expected the sky to be a different colour. Today America’s west coast continues to burn. According to California’s Department of Forestry and Fire Protection, wildfires in the state have consumed more than 4m acres this year, an area roughly the size of Connecticut. In Oregon and Washington, another 2m acres have gone up in flames. Last week California recorded its first “gigafire”: a single blaze that has scorched more than 1m acres.

The catastrophic fires have destroyed hundreds of homes and killed dozens of people. But they have also put surviving residents’ health at risk. At times, cities such as San Francisco, Portland and Seattle have suffered some of the most polluted air on the planet. Gavin Newsom, California’s governor, likened breathing the air in wildfire zones to “smoking 20 packs of cigarettes”. A recent study estimates that every additional microgram per cubic meter of daily PM2.5 (particulate matter less than 2.5 microns in diameter) exposure causes 0.69 additional deaths per million people aged 65 or over. Based on this calculation, Marshall Burke, Sam Heft-Neal and Michael Wara of the Stanford Institute for Economic Policy Research (SIEPR) estimate that poor air quality from this year’s wildfires will kill thousands of people, most of them elderly, in California alone. As wildfires become more common because of climate change, such deadly consequences will increasingly be felt across the country.

Mr Burke and his colleagues say that swift government action is needed. Pointing out that 60% of the area burnt by wildfires is on federal land, they recommend more “controlled burns”, where fires are deliberately lit, monitored and extinguished. This prevents the build-up of fuel such as dead trees, shrub and vegetable matter that, if ignited accidentally, might burn uncontrollably. They also argue that the rules governing wildfire emissions are counterproductive. Although wildfire smoke is counted as an “exceptional” emission, meaning that it is exempt from national air-quality standards, smoke from controlled burns is subject to stringent environmental regulations, creating further disincentives to using them. But even if this changes, America’s fire seasons are likely to get worse. Rising temperatures mean hotter and drier summers, which mean more violent and prolonged fire seasons. Unless global greenhouse-gas emissions are brought under control, this year’s terrifying wildfires will become the norm, not the exception.

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