Not for the first time this year, Californians this week donned face masks to protect their lungs from the harmful airborne particles that have smothered the state in a sickly, sooty haze. The pollutants are products of three devastating infernos raging hundreds of miles apart, the largest of which, Butte County's Camp Fire, has swelled to become the deadliest and most destructive in state history. They join the more than 7,500 California wildfires that have this year consumed nearly 1.7-million acres of land—more than any fire season on record. The increasing intensity of California's blazes has many residents of the Golden State wondering: Is the smoke from wildfires also getting worse?

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That's a complicated question. On one hand, data suggests California's fires are burning hotter and consuming more land than they did in the past. "If you use intensity as a proxy for pollution—that is, if you assume stronger fires will produce more emissions like smoke—then by dint of that, yes, there ought to be more smoke," says atmospheric composition scientist Mark Parrington.

A senior researcher at the Copernicus Atmosphere Monitoring Service, Parrington tracks wildfires around the world to better understand their effect on pollution and public health. Most mornings he's in his office by 8 am, downloading the previous 24 hours' worth of fire data from a supercomputer operated by the European Center for Medium-Range Weather Forecasts. The data—thermal infrared radiation measurements from NASA's MODIS instrument—allow him to estimate the intensity of fires burning around the world; how many emissions (like lung-aggravating aerosols and greenhouse gasses like carbon dioxide) they're pumping into the atmosphere; and how those emissions affect global air quality. From his office in Reading, just west of London, he's kept closer tabs on California's current wildfires than most. "You really don't expect to see emissions of this magnitude, this late in the year," Parrington says. "Even on a global scale, it really stood out."

Parrington also compares each day's emissions data to past measurements, which is how he knows that California's current wildfires have pumped more schmutz into the atmosphere than any November blazes on record. In fact, this year's California wildfires have produced more emissions than all but 13 of the past 16 years. "It's not just the Camp Fire, but the wildfires from this summer," Parrington says. "The Carr Fire, the Mendocino Complex Fire—they've been devastating." If the state sees any major wildfires in December (the way it did in 2017), 2018 could become the year with the highest emissions ever recorded for California.