SLATE - You know things have gone off the rails if people are arguing about whether it looks like Mars or Venus where they live. In case you missed it, fires are burning across the Western U.S., and thick wildfire smoke has enveloped regions of California and Oregon. As a result, residents of Salem and San Francisco are experiencing eerie orange-red skies.
As a result, air quality is also terrible across the West Coast. In Washington, where I live, the skies are hazy but mostly blue. Yet the Environmental Protection Agency’s numbers indicate worse air quality than in San Francisco, where the sky is completely red. That’s likely because the air quality index is a measure of surface air quality, says Roya Bahreini, an atmospheric scientist at University of California, Riverside. “The smoke from the wildfires can get injected higher in the atmosphere,” she says. In other words: That smoke might not affect surface-level measures of air quality, but it can, of course, still blot out the sun and filter light. And according to Daniel Swain, a UCLA climate scientist, smoke and ash are now traveling up to 50,000 feet—“20,000 above cruising altitude of jet airliners,” he wrote in a recent tweet. “Dense smoke throughout entire atmospheric column is blocking nearly all sunlight at surface.”