Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

SAN FRANCISCO — Wildfires in California in 2018 released the rough equivalent of about 68 million tons of heat-trapping carbon dioxide — about the same amount of carbon emissions as are produced in a year to provide electricity to the state, U.S. Interior Secretary Ryan Zinke said Friday.

The carbon dioxide figure — based on data analyzed by the U.S. Geological Survey — is more than 15 percent of all emissions produced by California in a year, according to Zinke.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

"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 included California's deadliest and most destructive wildfire — a blaze in November that took out nearly 14,000 homes in a rural Northern California county and killed at least 88 people. Another fire that started the same day in Southern California killed three people and destroyed 1,500 structures, including the homes of celebrities in tony Malibu.

Those two fires 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 the University of California, Los Angeles.

"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 that 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.