"We know that wildfires can be deadly and cost billions of dollars, but this analysis from the U.S. Geological Survey also shows just how bad catastrophic fires are for the environment and for the public's health," Zinke said in a statement.
This year, that included California's deadliest and most destructive wildfire in modern history — Butte County's Camp Fire that took out nearly 14,000 homes and killed at least 88 this month. Another fire that started the same day in Southern California, the Woolsey Fire, killed three people and destroyed 1,500 structures, including the homes of celebrities in tony Malibu.
Those two fires alone produced emissions equivalent to roughly 5.5 million tons of carbon dioxide, Zinke said.
The 2018 emissions figure for California wildfires is "strikingly high, significant in the context of overall statewide emissions, and likely a record value for single-year direct carbon emissions from wildfires in California history," said Daniel Swain, a climate scientist at UCLA.
"It is an alarming number, but we live in a fire-prone state," said Dick Cameron, director of science for land programs at the California chapter of the Nature Conservancy.
Zinke used the carbon figure he released Friday to continue to push for the thinning of forests. Cameron said it would help but that climate and home construction were also significant factors in the destructiveness of the fires.
Cameron cautioned that wildfire emissions were still a relatively small component of climate changing greenhouse gases. In California, cars and other transportation account for more than 40 percent of total emissions.