Fire & Climate
Smoke & Air Quality
The 2020 fire season in the western United States (the West) has been staggering: over 2.5 million ha have burned as of 31 September, including over 1.5 million ha in California (3.7% of the state), in part from five of the six largest fires in state history; over 760,000 ha have burned in Oregon and Washington, most occurring within a few‐day period (www.nifc.gov;(link is external) Figure 1a). The human impacts are unprecedented: millions have endured hazardous air, with estimates of thousands of smoke‐related deaths; over 10,000 structures have been damaged or destroyed, and dozens of lives have been lost. While fire is a fundamental natural process in most western ecosystems, these events have distinct human fingerprints—human‐caused ignitions, increased human exposure from expansion into flammable landscapes, increased fuel loads due to fire suppression, and increased fuel aridity due to climate change.