Nobody can yet say for certain exactly what ignited the deadliest and most costly wildfire in California history on October 8.
But climate scientists do know why conditions were tailor-made for the swift-moving maelstrom that killed 42 people, burned 6,700 homes and buildings, and blanketed millions of people in toxic smoke: Hotter temperatures; drier, abundant fuel; and stronger winds.
What caused all that? The answer is simple, obvious, and predictable: climate change.
Forty years ago, the average length of “fire season” in the western United States was about 138 days—the start of summer to the first winter rainfalls sometime in October. Now, says LeRoy Westerling, a professor at UC Merced and co-director of the school’s Center for Climate Communication, fire season in the West—the arid West, a vast inhospitable expanse made habitable for the white man's notion of civilization thanks only to the power and glory of irrigation—lasts 222 days.
“Fire season” is now another way to say “most of the year.”
This shift happened in our lifetimes. Since 1980, average global temperatures have escalated steadily and rapidly. Sixteen of the 17 warmest years on record have all come since 2001—and the world was noticeably hotter well before then. In that time, the areas burned by wildfires in the west have increased 390 percent—that is, “390 percent per decade, over that original baseline,” Westerling said during Tuesday's conference call. The probability of grasslands igniting has also increased significantly, from a 0.5 to 0.75 percent chance to a probability of between 1 and 2 percent.
You probably knew most of this, but what you may not know are the full ramifications or what to do about it.
How exactly did climate change cause the North Bay fires?
“Cause” is too strong a word. Warmer temperatures created the conditions for a fire to be more likely and more severe—and will continue to do so.
First, heavy winter rains after years of drought created an abundance of vegetation. Climate change leads to erratic weather patterns that are also more severe. A long, hot, and dry summer rendered this tinder-dry vegetation into what fire scientists and campfire-builders call “fuel.” And more heat also means more wind—and it was the Diablo winds, more and more similar to the Santa Ana winds in Southern California, gusting at times to more than 70 miles per hour, that spread the North Bay fires so quickly.
“Heat is what drives the wind in the first place,” said Dr. Bill Stewart, a specialist at UC Berkeley’s Center for Forestry.
How bad is the smoke, really?
Really, really bad. Wildfire smoke “is associated in numerous studies with increased premature death,” asthma, chest pain, and other “breathing problems, even in healthy people,” said Dr. Linda Rudolph, a public-health expert and director of the Center for Climate Change and Health at the Public Health Institute in Oakland. And, as most of the Bay Area witnessed over the past week, wildfire smoke travels long distances.
All this to say that wildfires are absolutely a problem for every Californian—all 40 million of us.
Can this happen here? By “here,” I mean (Los Angeles, San Francisco, Oakland, Hayward, insert name of city)?
Yes, certainly. We know this because it’s already happened here.
In 1991, more than 20 people died when wind-fanned flames torched the Oakland Hills. The behavior of the North Bay fires is “very similar to the Oakland Hills fire,” said Westerling.
The main difference there is that fire started from a single source. In Santa Rosa and the North Bay, there were possibly as many as 20 “starts,” as high winds carried embers far ahead of the fire line and ignited trees and other abundant dry fuel.
“If we had the wine country fire, more than 100,000 acres, that would be from Richmond to Hayward,” Westerling added. “And that is possible. We have more grasslands in those areas.”
The Oakland Hills fire showed that “it is not inconceivable to have a very, very large fire [in a more densely-populated area] when you have many starts,” Westerling said.
How quickly is our climate changing, really?
Do you like San Diego? If so, great, because Northern California’s ecosystem will more closely resemble the Southern California city in the coming years.
The state is on a trend where temperatures resemble places “one or two counties to the south” every decade, said Stewart. “Northern California, as it dries out, is acting more like Southern California. Hot fire weather is becoming more and more common way into the fall.”
Won’t that just mean fewer trees and desert-like conditions?
No, worse. It will mean more things to burn. “Shrubs do great in hot conditions,” Stewart said. “So do grasses.” And shrubs and grasses are both highly flammable, “the most flammable vegetation we have in California,” Stewart said. A shift to “warmer shrub land does not portend well for us.”
When will it end?
“This is part of a broader shift going on in our climate system that’s going to continue for some time—for the foreseeable future,” said Westerling. “Forest fires are going to continue to increase [in frequency and in severity] until fuel becomes more of a limitation.”
Even if we stabilize carbon emissions now, a task that will almost certainly require total regime change in Washington, D.C., “temperatures will keep increasing and the climate will keep changing for a while,” Westerling said. “This is part of what we have to learn to adapt to live with.”
How do we do that? What do we have to do?
Quite a bit, on all levels.
Future housing development will have to use fire-resistant materials and keep away from “wilder” areas with brush and vegetation. This is an issue, because, in many parts of the state, these are the areas we have to develop. Older homes will have to be retrofitted—and most of California’s housing stock is old.
We will also have to figure out how to warn people of an oncoming fire—and how to evacuate them much, much more quickly. In Santa Rosa, people had about one hour’s warning—and others, mere minutes that—to leave on winding rural roads choked with other evacuees. —to leave on roads choked with other evacuees.
Those of us in suburban and rural areas will also need protection beyond “a defensible fire line” around our homes or properties. A fire line won’t be much good if there are bushes or shrubs touching a home, a lawnmower with a gas canister parked near a porch, or a stack of firewood.
Making sure there’s nothing for flying embers to ignite “will be equally as important as defensible space,” noted Stewart.
Learn these words, policy wonks: “strategic vegetation management.” Much more care will have to be taken to clear shrubs and brush and other fuel away before it can torch another neighborhood. “California is probably underinvesting in how we’re doing strategic work in reducing vegetation that can burn,” he added.