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Sen. Mike Lee said Wednesday that the wildfires ravaging California and Oregon are not because of climate change, but from mismanagement by federal officials.

"Cycles of burning and regrowth are completely natural. They aren't a new feature of climate conditions as some would have us believe," Lee, an attorney by training and experience, said as he chaired a hearing on several bills by the Senate Energy and Natural Resources Subcommittee on Public Lands, Forest and Mining.

"These fires weren't unpredictable," Lee said. "In fact, they were predicted."

But he said bureaucratic rules have largely stopped such things as controlled burns to eliminate extra growth and fuel that could have prevented fires from burning hotter and spreading farther.

"Management of our forests has regrettably become hamstrung, partly by regulations promulgated by bureaucrats often operating many thousands of miles away from the lands that they're in charge of administering," he said.

Lee's comments are contradicted by many experts and scientists, who say the West Coast wildfires are incontrovertible evidence of climate change.

"The racing flames show how climate change is affecting the nation's most populous state, experts said," according to an article published Aug. 24 in Scientific American. "Hotter temperatures, less dependable precipitation and snowpack that melts sooner lead to drier soil and parched vegetation. Climate change also affects how much moisture is in the air," said Daniel Swain, a UCLA climate scientist.

"They [bureaucrats] may favor reactive short-term fire suppression at the expense of heightened long term risks," Lee complained.

Lee's point about the dangers of fire suppression are echoed by many experts, including Park Williams, a bioclimatologist at Columbia University's Lamont-Doherty Earth Observatory. But Park, quoted in Wednesday's New York Times, said the U.S. Forest Service in recent years has been trying to rectify the mistakes of the past through increased prescribed or "controlled" burns.

Lee blames the lagging use of controlled fires and other proactive measures on the threat of litigation.

"Management of our forests has moved away from proactive measure, largely out of fear ... of being sued," the Utah Republican said. "This, in turn, has led to bigger fires, threatening greater numbers of lives, livelihoods and homes."

Lee said research shows that fires in prehistoric California burned about 8 million acres each year. But men have cleaned out far less excess fuel in recent years.

"Between 1982 and 1998, California's agency of land managers burned on average 30,000 acres a year. Between 1999 and 2017, that number dropped to an annual 13,000 acres," he said. "That is a tremendous gap between the natural cycle and what our forest management efforts have provided."

Among many bills considered at the hearing was one by Lee to designate a mountain near Elk Ridge in Utah County as Miracle Mountain, because the fast-moving 2018 Bald Mountain wildfire miraculously stopped there and saved the city.

"This bill memorialized the events," Lee said. "Better forest management can reduce the severity of wildfires and reduce the risk to fire-prone communities. We need a range of management tools to cut the red tape and curb frivolous litigation that has stalled fuel reduction projects and efforts to remove dead and dying trees from poorly managed federal" lands.

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Utah Sen. Mike Lee says California wildfires caused by mismanagement, not climate change

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Sen. Mike Lee said Wednesday that the wildfires ravaging California and Oregon are not because of climate change, but from mismanagement by federal officials. "Cycles of burning and regrowth are completely natural.

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Climate change is driving the scale and impact of recent wildfires that have raged in California, say scientists.

Their analysis finds an "unequivocal and pervasive" role for global heating in boosting the conditions for fire.

California now has greater exposure to fire risks than before humans started altering the climate, the authors say.

Land management issues, touted by President Donald Trump as a key cause, can't by themselves explain the recent infernos.

See the devastation of the US wildfires in maps

Will Trump's rejection of climate science backfire?

The worst wildfires in 18 years have raged across California since August.

They have been responsible for more than 30 deaths and driven thousands of people from their homes.

The cause of the fires have become a political football, with California Governor Gavin Newsom blaming climate change for the conflagrations.

President Trump, on the other hand, has dismissed this argument, instead pointing to land management practices as the key driver.

Now, a review of scientific research into the reasons for these fires suggests rising temperatures are playing a major role.

Earlier this year, the same research team published a review of the origins of Australia's dramatic fires that raged in the 2019-2020 season.

That study showed that climate change was behind an increase in the frequency and severity of fire weather - defined as periods of time with a higher risk of fire due to a combination of high temperatures, low humidity, low rainfall and high winds.

How we outran a California wildfire

Is Trump right about the cause of US wildfires?

The new review covers more than 100 studies published since 2013, and shows that extreme fires occur when natural variability in the climate is superimposed on increasingly warm and dry background conditions resulting from global warming.

"In terms of the trends we're seeing, in terms of the extent of wildfires, and which have increased eight to ten-fold in the past four decades, that trend is driven by climate change," said Dr Matthew Jones from the University of East Anglia in Norwich, UK, who led the review.

"Climate change ultimately means that those forests, whatever state they're in, are becoming warmer and drier more frequently," he told BBC News.

"And that's what's really driving the kind of scale and impact of the fires that we're seeing today."

In the 40 years from 1979 to 2019, fire weather conditions have increased by a total of eight days on average across the world.

However, in California the number of autumn days with extreme wildfire conditions has doubled in that period.

The authors of the review conclude that "climate change is bringing hotter, drier weather to the western US and the region is fundamentally more exposed to fire risks than it was before humans began to alter the global climate".

The researchers acknowledge that fire management practices in the US have also contributed to the build-up of fuel.

Normally, fire authorities carry out controlled burnings in some areas to reduce the amount of fuel available when a wildfire strikes - but these have also suffered as a result of rising temperatures.

"When you do prescribed burns, you can only do it when the conditions aren't too hot and dry, because you need to be able to control the fire," said Prof Richard Betts from the UK Met Office and the University of Exeter who was part of the review team.

"But once you've passed the point where you've got hot, dry conditions for much of the year, you've lost your opportunity to do lots of prescribed burnings. So that makes matters worse and makes the land management challenge even greater."

Another factor in California has been the encroachment of human settlements into forested areas. This has put many more homes at risk of these blazes.

Between 1940 and 2010, there was around a 100-fold increase in the number of houses built in dangerous fire zones in the western US.

"It's like building on floodplains as well, you know, people are putting themselves in harm's way, based on past statistics, which are no longer true," said Prof Betts.

"The past is no longer a guide to the future, for flooding and for fire and lots of other ways in which climate change is played out."

The researchers say that the conditions for wildfire are likely to continue to grow into the future, and according to Dr Jones, the resulting fires will likely get worse.

"It's pointing towards increases in fire weather that become increasingly intense, widespread and dramatic in the future," he said.

"And the more that we can do to limit the degree to which temperatures rise, is fundamental to how frequently we see dangerous fire weather in the future."

Full details of the review can be found here.

Follow Matt on Twitter.

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Clear climate link to California wildfires - study

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Climate change is driving the scale and impact of recent wildfires that have raged in California, say scientists. Their analysis finds an "unequivocal and pervasive" role for global heating in boosting the conditions for fire. California now has greater exposure to fire risks than before humans started altering the climate, the authors say.

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CBS journalist Scott Pelley recently visited Butte County, California, to report on the wildfires devastating the Golden State.

Government statistics show that more than 8,300 wildfires have burned some 4 million acres to date. The flames have claimed 31 lives and destroyed nearly 8,700 structures. One of those structures belonged to Fire Station 61 Chief Reed Rankin, who saw his home reduced to a charred skeleton after a September blaze.

"[It's] nothin' but a foundation with a metal roof on top of it," Rankin, who has spent more than 28 years as a firefighter, told Pelley. "It's completely burned down."

CBS had a wonderful opportunity to explore the devastating impact and causes of California's fires. Unfortunately, it was an opportunity missed. The 60 Minutes segment focused primarily on climate change, a topic that is covered in depth virtually every single day.

California's historic wildfires received scant attention, and all but the most attuned viewers would have concluded that the wildfires are simply the result of global warming. That's because Pelley spent a total of seven seconds of the 13-minute segment explaining a primary cause of California's megafires.

"Climate isn't the only reason," Pelley says of the wildfires at one point. "Decades of aggressively putting out every forest fire allowed brush to pile up like kindling."

Pelley is correct. There is a widespread scientific consensus that California's aggressive efforts to suppress fire have made the state ripe for megafires. But this is the last 60 Minutes viewers hear on the mismanagement of California's forests.

The bulk of the segment is dedicated to interviewing James Hansen and Michael Mann, a pair of scientists who have spent decades warning about the dangers of man-made climate change.

"We're seeing exactly what we expected," said Hansen, who in 1988 produced a seminal paper predicting a decades-long rise in global temperatures. "But I expected that governments would be wise enough that they'd begin to adopt policies to preserve the future for young people. But they haven't done that yet."

Hansen runs the program on climate science at Columbia University, and Pelley notes that he is considered the "father of climate change science."

"If we don't change anything, then we're going to continue to see more and more of these extreme regional events," Hansen says. "The physics is quite simple. As you add more greenhouse gasses to the atmosphere, you increase the heating of the surface. So at the times and places where it's dry you get more extreme droughts, the fire seasons become longer, the fires burn hotter."

When I first wrote about California's wildfires, I noted that evidence suggests both poor land management and California's high temperatures have played a role in the wildfires. And it's certainly reasonable to assume the dry and hot conditions have contributed to California's harsh season.

Yet to blame the bulk of the blame on climate change ignores evidence that suggests government policies are the primary culprit. Consider these facts.

1. Wildfires are not at historic highs (not even close)

It's true that California is suffering from a truly devastating fire season, one that has exacted a sadly high toll on human lives. Across the US, however, burning is much lower than previous decades.

As of October 5, fires have consumed 7.8 million acres of land in the US over the last year. That's less over the same period that burned in 2017, 2015, 2012, and 2011. Moreover, it's a small fraction-about 1/4th-of the yearly average between 1926 and 1952, according to the official historical data.

When journalists and climate activists warn of record-high levels of fire in the US, they're simply ignoring all data prior to 1960. This offers a politically convenient baseline, since it means that the data set begins when fire suppression was still a widely used management tool in the US.

For all the talk about 2020's fires being an unprecedented apocalypse (7M acres burned), it's worth noting 2020 is unlikely to surpass 2017's total.

Even if it does, it's still about about 1/5 of the total acreage burned in 1930.

Context matters. H/T @BjornLomborg. pic.twitter.com/x44Ag1l4me
- Jon Miltimore (Parler: @Miltimore79) (@miltimore79) September 21, 2020

2. California is 4.3% of US landmass-but has 50% of its burn area in 2020

State statistics say California has seen about 4 million acres burn this season. That's a lot. In fact, it's more than half of the total acreage burned in the US.

To be sure, California is a really big state-163,694 square miles. But that's still just 4.3 percent of the total land area of the US.

What these numbers mean is that the megafire problem in the US right now is a problem pretty much singular to California. This suggests it's less about climate change and more a result of the state's decades-long practice of fire suppression.

As fire experts recently told the New York Times, other parts of the United States long ago abandoned such policies, recognizing natural and prescribed burning are effective tools to manage the land.

"Today fire is widely accepted as a tool for land management in the Southeast," said Crystal Kolden, a fire scientist at the University of California, Merced, told the Times last month.

Is it possible that Appalachia country and other parts of the US are being spared from the effects of climate change? More likely, they simply learned decades ago a fact that California has refused to acknowledge: burning is necessary, and aggressive efforts to suppress it are disastrous.

California represents 4.3% of US landmass but accounts for more than 50% of its burned acreage in 2020.

Does climate change effect California differently than other parts of the country?

Or are we seeing the results of Calif's aggressive, decades-long fire suppression tactics?
- Jon Miltimore (Parler: @Miltimore79) (@miltimore79) October 6, 2020

3. Texas is Hotter Than California and Has More Forests, but Far Fewer Megafires

In case some people do believe that California is simply experiencing harsher effects of climate change than other parts of the country, it's worth pointing out a few simple geographical facts about Texas.

The Lone Star state actually has more forest area than the Golden State and higher temperatures. Yet government data show they've had far fewer megafires. From 1997-2019 Texas had about one third the number of megablazes (fires larger than 100,000 acres) that California did.

What could explain these results? Perhaps the fact that 95 percent of Texas's land mass is privately owned and authorities have embraced burning policies that allow fire to do its natural work.

Texas has more forest than Calif. and higher temps, yet gov. data show show that from 1997-2019 TX had about 1/3 the number of megablazes (fires larger than 100k acres) that California did.

-95% of Texas' land mass is privately owned.
-Texas embraces natural burning, unlike CA. pic.twitter.com/nsM95D0vrB
- Jon Miltimore (Parler: @Miltimore79) (@miltimore79) October 6, 2020

California's wildfires are a serious matter. We must make every effort to protect people and communities from their devastating effects. But the crisis should not be used to advance a politicized climate change agenda, especially when evidence suggests California's wildfires stem largely from government mismanagement.
Additional Reading: Forest Fires Aren't at Historic Highs in the United States. Not Even Close They Know How to Prevent Megafires. Why Won't Anybody Listen? Why There Are So Many Wildfires in California, but Few in the Southeastern United States Federal Regulations Have Made Western Wildfires Worse
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3 Inconvenient Truths 60 Minutes Forgot to Mention in Its Story on California Wildfires and Climate Change | Jon Miltimore

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California represents 4.3 percent of US landmass but accounts for more than 50 percent of its burned acreage in 2020. This invites an important question: Why are megafires such a big problem in the Golden State compared to the rest of the country?

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Many blame climate change for California's fires, but the main causes lie elsewhere
Associated Press

In 2018, a fire ripped through the town of Paradise, California, killing 85 people. It was the deadliest and most destructive wildfire in the state's history.

Liabilities from wildfires started by its powerlines bankrupted Pacific Gas & Electric, which cut off power to nearly one million homes and businesses last month to prevent wind from triggering and fanning fires.

Many blame climate change."The reason these wildfires have worsened is because of climate change," said Leonardo DiCaprio."This is what climate change looks like," said Rep. Alexandria Ocasio-Cortez.

On Sunday, after President Donald Trump tweeted, "The Governor of California, @GavinNewsom, has done a terrible job of forest management," Newsom tweeted back, "You don't believe in climate change. You are excused from this conversation."

But can the increase in fires in California really be blamed on climate change?

I asked Dr. Jon Keeley, a US Geological Survey scientist who has researched the topic for 40 years, if he thought the 2018 Paradise fire could be attributed to climate change.

"It's almost certainly not climate change," he said. "We've looked at the history of climate and fire throughout the whole state, and through much of the state, particularly the western half of the state, we don't see any relationship between past climates and the amount of area burned in any given year."

Much else in the media's coverage of the issue has been misleading if not outright wrong, including the suggestion that 2019 is comparable to 2017 and 2018. "Three years in a row feels like - well, it starts to feel like the new, and impossible, normal," said climate activist-journalist Bill McKibben in The Guardian.

"We've had some unbelievable fire years the last couple of years," said Hugh Safford, a forest ecologist with the US Forest Service. "This one has not been nearly as bad yet, even with this outbreak of fires over the last week and a half."

All of the scientists I interviewed expressed frustration that journalists have failed to distinguish between two distinct types of fires.

"The media haven't gotten the idea that we have two very different fire problems," Keeley said. "And so the politicians haven't been reading about the two very different problems."

The first is the wind-driven fires on coastal shrubland, or chaparral, where most of the houses are. Think: Malibu and Oakland. Nineteen of the state's 20 most deadly and costly fires were there.

The second is the forest fires in places like the Sierra Nevadas where there are far fewer people.

Mountain ecosystems have the opposite problem from coastal ones. There are too many fires in the shrublands and too few prescribed burns in the Sierras.

Keeley refers to the Sierra fires as "fuel-dominated" and the shrubland fires as "wind-dominated."

The on solution to fires in the shrubland is to prevent them and/or harden homes and buildings to them.

Before Europeans arrived, fires burned up woody biomass in forests every 10 to 20 years, preventing the accumulation of (wood) fuel, and burned in the shrublands every 50 to 120 years.

But for the last 100 years, the US Forest Service (USFS) and other agencies put out most fires, resulting in the accumulation of wood fuel. "It's like the forests have become a really tall version of chaparral," said Safford.

The result can be fires that burn so hot they sometimes kill the forest, turning it into shrubland.

"I did a paper that found if you looked at Sierra Nevadas you'd want a half-million acres a year burned," said US Forest Service research ecologist, Malcolm North. But, "over a 10-year period, the Forest Service was treating 28,000 acres and burning 7,000 acres, and so we're at just seven to eight percent of where you would want to be."

In 2006, scientists predicted climate change would increase the east-to-west blowing winds, worsening these coastal fires, but in 2011 and again in 2019 scientists predicted they would decrease.

"Some will argue that it's climate change but there is no evidence that it is," said Keeley. "It's the fact that somebody ignites a fire during an extreme [wind] event."

The scientists emphasize that higher temperatures from climate change may be contributing to fire risk in the Sierras. "Fire season has lengthened 50 - 80 days per year," notes North, "and that definitely has a signature to it from changing climatic conditions."

But, North adds, "We want to pay particular attention to the fuels. It's really the one way we've got to change fire patterns because we can't change the climate."

Keeley published a paper last year that found that all ignition sources of fires had declined except for powerlines.

"Since the year 2000 there've been a half-million acres burned due to powerline-ignited fires, which is five times more than we saw in the previous 20 years," he said.

"Some people would say, 'Well, that's associated with climate change.' But there's no relationship between climate and these big fire events."

What then is driving the increase in fires?

"If you recognize that 100% of these [shrubland] fires are started by people, and you add 6 million people [since 2000], that's a good explanation for why we're getting more and more of these fires," said Keeley.

What about the Sierras?

"If you look at the period from 1910 - 1960," said Keeley, "precipitation is the climate parameter most tied to fires. But since 1960, precipitation has been replaced by temperature, so in the last 50 years, spring and summer and temperatures will explain 50% of the variation from one year to the next. So temperature is important."

Isn't that also during the period when the wood fuel was allowed to build due to supression of forest fires?

"Exactly," said Keeley. "Fuel is one of the confounding factors. It's the problem in some of the reports done by climatologists who understand climate but don't necessarily understand the subtleties related to fires."

So, would we have such hot fires in the Sierras had we not allowed fuel to build-up over the last century?

"That's a very good question," said Keeley. "Maybe you wouldn't."

He said it was something he might look at. "We have some selected watersheds in the Sierra Nevadas where there have been regular fires. Maybe the next paper we'll pull out the watersheds that have not had fuel accumulation and look at the climate fire relationship and see if it changes."

I asked Keeley what he thought of the Twitter spat between Gov. Newsom and President Trump.

"I don't think the president is wrong about the need to better manage," said Keeley. "I don't know if you want to call it 'mismanaged' but they've been managed in a way that has allowed the fire problem to get worse."

What's true of California fires appears true for fires in the rest of the US.

In 2017, Keeley and a team of scientists modeled 37 different regions across the US and found "humans may not only influence fire regimes but their presence can actually override, or swamp out, the effects of climate."

Of the 10 variables, the scientists explored, "none were as significantly significant... as the anthropogenic variables."

I asked Keeley if the media's focus on climate change frustrated him.

"Oh, yes, very much," he said, laughing. "Climate captures attention. I can even see it in the scientific literature. Some of our most high-profile journals will publish papers that I think are marginal. But because they find climate to be an important driver of some change, they give preference to them. It captures attention."

... Read More

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Why Everything They Say About California Fires - Including That Climate Matters Most - Is Wrong

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In 2018, a fire ripped through the town of Paradise, California, killing 85 people. It was the deadliest and most destructive wildfire in the state's history. Liabilities from wildfires started by its powerlines bankrupted Pacific Gas & Electric, which cut off power to nearly one million homes and businesses last month to prevent wind from triggering and fanning fires.

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California wildfire activity has been increasing for the last 50 years, and the dominant driver of the increase is warming that is "very likely human-caused climate change," he said.

For years, scientists have said that climate change is baking California's forests, but the wildfires are also driven by other factors, including forest management techniques and natural climate variation.

Disentangling all the wildfire drivers is complicated, but Williams calls climate change "decisive."

Also, the new research suggests that arid and hot conditions, in particular, were key reasons for the devastating forest fires that burned in recent years. The Tubbs fire killed 22 people and burned 36,807 acres in 2017, and last year's Camp Fire killed 85 people and torched an incredible 153,336 acres.

The two fires are the worst on record in California. Of the top 20 most destructive California wildfires, 10 have occurred since 2015. Of the top 10, seven have burned over the last four years.

"When we compare the records of forest fire areas in California against all the variables out there, the strongest correlation by far is the aridity of the atmosphere, and that's driven by temperature," said Williams.

Meg Krawchuk, a fire ecologist at the College of Forestry at Oregon State University, said the study is a thorough assessment of relationships between area burned and climate.

"It is incredibly important for all of us living in areas vulnerable to wildfire to more thoroughly appreciate how climate, and anthropogenic climate change more specifically, is contributing to the fires we're experiencing in recent decades," said Krawchuk, who was not involved in the study.

Jon E. Keeley, a fire scientist with the US Geological Survey, said he agrees that rising temperatures are drying out forests and playing a major role in the increase in wildfire activity during the summer. "The hot air dries out fuels and makes the forests more flammable," he said.

But he disagrees with another portion of the paper that emphasized the role that climate change plays in coastal and Southern California. He said the problem is that people there are starting more fires, either intentionally or with infrastructure like power lines.

"When it comes to fire, climate is important but it's not the only show in town," said Keeley, who did not participate in the study. "I think the real issue is population growth. We've added 6 million more people in the last 18 years, you can't overlook that and address that as an important factor. The increases in fire are, in large part, due to ignition during extreme wind events."

To be sure, there are many reasons that fire threatens to unleash disaster and chaos in more California communities.

For one, forest managers suppress naturally-occurring fires. Federal agencies resist performing prescribed burns in California when they're needed, which would curb the risk of wildfire.

Also, as wildfire-susceptible areas expand statewide, new Californians keep pouring into them. By midcentury, home builders may add as many as 1.2 million new units in geographic areas most at risk.

Those are major factors, but Williams reiterates that a warming climate is the most powerful lever. As the atmosphere heats up, it acts like a sponge, soaking moisture out of the state's forests -- which increases the risk of a fire.

The warmer the atmosphere gets, the more moisture it can pull out of forests. Each degree of warming does more to promote fire than the previous degree, according to Williams, who said that large fires are likely to become increasingly frequent with continued warming.

Californians can learn to survive wildfire in a warming world. It will mean big changes in how we think and live. Read some of the stories of people leading the way in communities across the state here.

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Study: Climate Change a Leading Driver of California's Wildfires | KQED

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California wildfire activity has been increasing for the last 50 years, and the dominant driver of the increase is warming that is "very likely human-caused climate change," he said. For years, scientists have said that climate change is baking California's forests, but the wildfires are also driven by other factors, including forest management techniques and natural climate variation.

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Jon Keeley

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As of late October more than a dozen wildfires north of San Francisco had killed more than 40 people, burned approximately 160,000 acres and destroyed more than 7,000 structures.

This tragic loss of life and property is unprecedented in California. However, the fires are not anomalous events in terms of their size, intensity or the speed with which they spread. Indeed, the path of the destructive Tubbs fire in Napa and Sonoma counties mirrors that of the Hanley fire of 1964. This extreme wind-driven fire burned under similar conditions, across much of the same landscape and covered an area substantially greater than the recent Tubbs fire.

Strikingly, though, no lives were lost during the Hanley fire and only 29 structures were destroyed. Why did these two fires, 50 years apart, burn on the same general landscape, under similar extreme winds, with such different human impacts? Fire scientists will study these events intensively to parse out the relative importance of various factors. But it is clear that two factors probably were major contributors: wind and population growth.

NASA Earth Observatory

Driven by Diablo winds

The Tubbs fire began on the night of Oct. 8 near Calistoga in Sonoma County under extreme fire weather conditions, with high winds and low relative humidity. Normally, winds in this region flow from the west, carrying cool, humid air from the ocean onshore. These winds reversed that pattern: They blew out of the northeast at 40 miles per hour, with gusts up to 75 miles per hour. Such winds are common in California during the autumn, and are known as Diablo, Mono or North winds in Northern California and Santa Ana winds in Southern California.

These hot, dry winds develop from an unusual pattern of high and low pressure cells, and are most prominent in autumn. They follow the normal summer and fall drought that occurs in this Mediterranean-type climate, leading to severe fire weather conditions. Such winds are associated with some of the most catastrophic fires in California's history. In the San Francisco Bay area, they played a role in the 1991 Tunnel fire, where wind gusts of 60 miles per hour were responsible for 25 deaths, even though the fire measured only slightly over 1,000 acres. The speed of these fires is a major factor leading to the loss of human lives.

Since fires in Northern California do not appear to have changed in this 50-year period, what accounts for the difference in impact? Certainly one critically important factor is demography. California's population has more than doubled in the past 50 years, but Santa Rosa, which was hit hard by the Tubbs fire, has five times as many people as it did in 1964.

CA Dept of Finance

Population growth

This dramatic growth can affect fire losses in several ways. Nearly all fires in Sonoma County are caused directly or indirectly by people, such as intentional ignitions or power lines igniting fires. Population growth raises the probability of fire igniting under severe weather conditions. More frequent human-caused fires also convert woody vegetation to more abundant herbaceous vegetation, which increases ignition probability and the rate of fire spread.

Population growth also spurs urban expansion. Development has spread outward, positioning people closer to watersheds of dangerous fuels. These fires burned through grasslands, oak woodlands and dense stands of chaparral shrublands that last burned 50 years ago. Diablo winds are often funneled by particular topographic features, such as low-lying passes in mountains. This makes some parts of the landscape, which fire experts refer to as wind corridors, more vulnerable than others.

The so-called wildland-urban interface, or intermix, where development and wildland vegetation meet, is where most homes are destroyed by fires. Data presented at a recent Senate Science Forum show that both high- and low-density development in the areas where the California wine country fires occurred have expanded dramatically in the last several decades.

Jennifer Kakareka Balch, Bethany Bradley, Author provided (No reuse)

What about climate change?

Many accounts increasingly see climate change as a contributing factor in big fire events. There is good evidence that climate change will increase fires in some western forests, but there is little evidence that it will play a similar role in coastal California.

In a recent study, we examined over 100 years of California climate records and examined the extent to which higher temperatures in different seasons might have contributed to enhanced fire activity, and found that there was very little correlation in coastal California. We hypothesized that this was likely because in lower elevations, temperatures are sufficient to lead to large fire events in most years, and fires are more strongly controlled by the timing of human ignitions in association with extreme winds.

Some reports have suggested that widespread tree deaths helped fuel the recent firestorm. The extreme drought of 2012-2014 caused extensive tree deaths, but most mortalities occurred farther east, in California's Sierra Nevada mountains. In coastal counties, in contrast, many trees have been killed by sudden oak death syndrome, a disease spread by an exotic fungal pathogen.

However, according to the California State Tree Mortality Database, there were few dead trees within the fire perimeters in wine country. And in some instances fierce winds carried the fire to communities that were a mile or more away from dangerous wildland fuels such as dead trees. These facts imply that tree mortality played a minimal role in the destruction caused by this firestorm.

Still another potential factor is above-normal rainfall during 2017. High rainfall increases plant growth in grasslands, which leads to increased fire incidence and spread. In all likelihood this did play some role.

AP Photo/Ellen Knickmeyer

Human factors

Looking to the future, fire-climate studies in coastal California have concluded that in this coastal region, direct human impacts are likely bigger concerns than indirect impacts from climate change.

On the plus side, this suggests that there is great potential for altering fire outcomes by reducing fire ignitions. We do not yet know what ignited this year's Northern California fires, but extensive experience within the state points to several likely culprits: downed power lines, arson, debris burning and equipment such as generators.

Since these fires started at night, debris burning and equipment seem to be less likely causes. However, there were reports of extreme winds blowing down power lines, and historically such events have started some of California's worst fires.

Current U.S. Geological Survey research indicates that during the last several decades there has been a significant decline in arson-ignited fires in California and a decline in area burned due to arson. In all likelihood, increased fire prevention strategies have played a role in this decline. On the other hand, power line fires have not declined in number or area burned in the last several decades, and ignitions from power lines remain a statewide problem. Actions that can reduce the risk of this ignition source can include placing power lines underground.

Drought and warmer climates have made wildfires a year-round hazard in California. Expanded urban development, in tandem with hot winds, seems to be the primary reason for the destruction this year. Once we better understand what factors made the 2017 fires so damaging, communities can prepare for future outbreaks in this increasingly fire-prone landscape.

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Why were California's wine country fires so destructive?

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As of late October more than a dozen wildfires north of San Francisco had killed more than 40 people, burned approximately 160,000 acres and destroyed more than 7,000 structures. This tragic loss of life and property is unprecedented in California. However, the fires are not anomalous events in terms of their size, intensity or the speed with which they spread.

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Jon Keeley

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Jon Keeley

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Significance

Projections of worsening wildfire conditions under climate change are a major concern in policy and management, but there is little understanding of geographical variation in fire-climate relationships. Our analysis relating climate variables to historical fire activity across the United States showed substantial variability in the importance of different seasonal temperature and precipitation variables and of climate overall in explaining fire activity. Climate was significantly less important where humans were more prevalent, suggesting that human influence could override or even exceed the effect of climate change on fire activity. Although climate change may play a significant role in altering future fire regimes, geographical context and human influence should also be accounted for in management and policy decisions.

Abstract

Growing human and ecological costs due to increasing wildfire are an urgent concern in policy and management, particularly given projections of worsening fire conditions under climate change. Thus, understanding the relationship between climatic variation and fire activity is a critically important scientific question. Different factors limit fire behavior in different places and times, but most fire-climate analyses are conducted across broad spatial extents that mask geographical variation. This could result in overly broad or inappropriate management and policy decisions that neglect to account for regionally specific or other important factors driving fire activity. We developed statistical models relating seasonal temperature and precipitation variables to historical annual fire activity for 37 different regions across the continental United States and asked whether and how fire-climate relationships vary geographically, and why climate is more important in some regions than in others. Climatic variation played a significant role in explaining annual fire activity in some regions, but the relative importance of seasonal temperature or precipitation, in addition to the overall importance of climate, varied substantially depending on geographical context. Human presence was the primary reason that climate explained less fire activity in some regions than in others. That is, where human presence was more prominent, climate was less important. This means that humans may not only influence fire regimes but their presence can actually override, or swamp out, the effect of climate. Thus, geographical context as well as human influence should be considered alongside climate in national wildfire policy and management.

Fire-Climate Relationships Varied Geographically in the Importance and Strength of Different Seasonal Climate Variables

There was wide geographical variation in the independent influence of seasonal temperature and precipitation variables on annual fire activity, not only across NEON domains but also across federal agencies ( Fig. 3), as well as in comparison with the full-region analyses using FPA FOD data ( Fig. 3). There were no strong patterns across latitudinal or longitudinal gradients, but the influence of prior-year precipitation was generally most important in western regions, except for a clear contribution to fire activity in the Appalachian, Mid-Atlantic, and Northeastern regions. Temperature variables were more important than precipitation variables in NPS lands versus USFS lands, but the effect of temperature versus precipitation was more equally, yet unsystematically, distributed across BLM lands and full NEON domains. In terms of seasonal importance, spring and summer temperature and precipitation variables overall explained more independent variation in fire activity than autumn or winter variables.

The results of the multiple-regression analyses showed that the average variance in fire activity explained by climate for the 37 federal regions was 29%. Climatic variables explained ≥50% variation in fire activity in five regions ( Table S1), only one of which was located in the eastern United States, the Appalachian region on USFS lands. Here, fire activity was primarily explained by low precipitation in all seasons except for summer, plus high spring temperature. The other four regions with the strongest fire-climate relationships were the Southern Rockies on NPS lands, the Pacific Southwest on USFS lands, and the Great Basin and Northern Rockies on BLM lands. In all four of these regions, prior-year precipitation was among the variables included in the top-supported models, and the relationship was negative for all but the Great Basin where it was positive. Maximum summer temperature was the other variable that was included in all four of the western regions with the strongest fire-climate relationships, and maximum spring temperature was additionally important in the Southern and Northern Rockies.

In the multiple-regressions using the FPA FOD data, the average variance in fire activity explained by climate was 42%, and in these data, there were six regions where climate explained >50% of the variation in annual fire activity ( Table S2). These regions were either in the Southeast, Midwestern United States (Northern Plains, Prairie Peninsula, Ozarks Complex), or western United States (Northern Rockies, Great Basin). For these regions, high summer or winter temperatures were consistently important in the western regions and the Northern Plains, whereas hot spring and summer maximum temperatures were more important in the Prairie Peninsula or the Southeast. Low spring or summer precipitation was also important in these regions.

The Importance of Climate Overall Varied Across Regions

The overall strength of fire-climate relationships varied substantially across the continental United States, both in terms of longer-term federal fire records and the shorter-term, more spatially comprehensive FPA FOD fire data ( Fig. 4). Although climate variables explained >50% of the variation in fire activity in some regions, as described above, 10 of the 37 regions in the federal analysis and four of the regions in the FPA FOD analysis had adjusted R ² values signifying ≤15% of the variance in fire activity could be explained by climate.

Human Presence Was the Only Factor to Significantly Explain Differences in the Strength of Fire-Climate Relationships

Of the 10 different variables we explored to explain the variation in the strength of fire-climate relationships, none were statistically significant at P ≤ 0.05 except for the anthropogenic variables ( Table 1 and Figs. S1 and S2). In the federal data, regions in close proximity to either roads or developed areas had weaker fire-climate relationships; and in the FPA FOD data, regions with a higher mean human population and proportion of developed land had weaker fire-climate relationships.

Discussion

Seasonal climate variation has played a significant role in explaining annual fire activity across the continental United States, but the relative importance of different variables, in addition to the overall importance of climate, varies substantially depending on geographical context. Why climate explains more fire activity in some regions than others is best explained by human presence. That is, in regions where human presence is more prominent, the importance of climate is lower on average. This suggests that, not only can humans influence fire regimes, as has been documented, but their presence can actually override, or swamp out, the effect of climate. This has serious implications for national fire policy and management as we move forward in this era of rapid global change.

Humans can affect wildfire patterns in a number of ways, from starting fires to managing fires (e.g., prescribed fire or fire suppression) and via changes in the abundance and continuity of fuel through land use decisions. For example, humans alter native vegetation through agriculture, urbanization, and forestry management practices. Although their geographical subdivisions were coarser than those used here, regions where lightning-started fires dominated in a recent nationwide analysis ( 27) show some alignment with areas here where fire-climate relationships were stronger, largely in the interior, northwestern part of the country. Nevertheless, although human-caused ignitions predominate across most of the country, there are also regions like the interior Southeast where fire-climate relationships were relatively strong but the cause of ignitions was nevertheless dominated by humans.

This suggests that human influence goes beyond just starting fires, and there is some combination of factors that leads to a dampening of the effect of climate on fire activity. This may be due to effective lengthening of the fire season ( 27), or starting fires in areas where naturally occurring fires are rare. On the other hand, fragmentation of fuels via land use and urban development may interrupt the spread of fires that would otherwise occur in a less human-dominated landscape. In this case, the climatological factors that might otherwise lead to fire spread are overridden by human-created landscape patterns. This dual effect of humans either increasing fire where it would not otherwise occur, or decreasing it where it would occur, may be why the overall amount of fire in a region was not significantly related to the importance of climate. A couple of other studies performed at smaller extents also suggest that human influence [i.e., suppression policy ( 40) or land use ( 33)] in addition to fuel quantity or quality ( 31, 33) can potentially mediate or dampen fire-climate relationships across different temporal scales.

One of the most consistently important variables for explaining strong fire-climate relationships was prior-year precipitation, which is similar to results in other studies (e.g., refs. 28, 30, and 35). This relationship is often found in grasslands and savannahs where fire activity is fuel-limited. High precipitation appears to have a dampening effect on current-year fires but leads to high fuel loads in subsequent years, and the production of fine-fuel biomass that dries by the following year is conducive to fire spread ( 41). In forested ecosystems, this relationship has been shown to be present in forest types with herbaceous understories and absent in ones with understory fuels comprising litter and other downed material ( 42).

An important caveat to this study is the fact that the variance explained for the differences in strength of fire-climate relationships was not particularly high, and there was substantial variability in the data ( Figs. S1 and S2). Therefore, despite evaluating the role of climatic or topographic variability, or variation in vegetation or forest biomass, differences in strength of fire-climate relationships may be due to additional factors. For example, temperature or precipitation patterns may be less variable in some regions than in others, meaning there is less annual variability in fire activity due to these variables. Another reason may be that the fire-climate models do not include essential factors such as localized fire-weather events, long-term drought, or lightning density, nor do they account for variable interactions or more complex variable combinations.

The record of fire history was only available spatially since the 1970s, and a longer-term history could have provided a more robust analysis. However, fire-climate relationships do vary over long time scales ( 33, 35, 40), and the findings here are representative of the most current conditions. These results thus provide important insight on contemporary drivers of fire activity across a time when climate has already been changing rapidly ( 43).

Climate change may indeed be a concern for those areas with strong fire-climate relationships. However, our results suggest that, in some areas, anthropogenic factors diminish the influence of climate on fire activity. Thus, to effectively understand how and where fire regimes may change in the future, anthropogenic factors must become a larger part of the conversation relative to national fire policy and management. In addition to incorporating anthropogenic factors such as land use into future fire projections ( 44), it will also be important to consider alternative management decisions in the context of human development. For example, land use or conservation planning decisions have the potential to alter fire risk to structures as well as biodiversity outcomes ( 45, 46). Further work on fire prevention strategies is another important avenue for future fire management and is likely to play very different roles on different landscapes.

Materials and Methods

To develop our historical fire data, we assembled a comprehensive point-based spatial database of more than a million fires on federal agency lands. The more contemporary database beginning in 1992, the national interagency FPA FOD ( 47), provides more spatially extensive data that span all public and private lands. (See SI Text for additional details on data sources, assembly, and modeling.)

We used monthly PRISM 2.5 arc-minute historical climate data ( www.prism.oregonstate.edu/) to derive and extract seasonal climate means to relate to annual fire data for NEON regions and for fire locations within those regions from 1972 to 2010. We defined winter as December through February, spring as March through May, summer as June through August, and autumn as September through November.

To quantify the relative and geographically varying importance of different climate variables in explaining fire activity, we used a hierarchical partitioning algorithm available in R (hier.part package, version 1.0-4 in R) ( 48, 49). Hierarchical partitioning, via a hierarchy of regression models using all combinations of explanatory variables, calculates the percentage of independent influence of each variable on the response, with or without its joint influence via other variables. Thus, it avoids issues of multicollinearity and provides a discrete quantification of relative variable importance. In addition to quantifying variable importance, we also developed multivariate models for the regions to account for the overall importance of climate in explaining annual fire activity. For every region, we selected the best-supported model, recorded the variables, and calculated the adjusted R ² as a measure of total variance explained by climate.

To identify potential factors explaining the variation in strength of fire-climate relationships, we summarized a range of biophysical and human variables ( Table 1) across the geographical extent of each region and related them to the adjusted R ² values described above using bivariate linear regressions.

Acknowledgments

We thank Lou Pitelka for convincing us of the value of utilizing NEON domains in our study. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the US government.

Footnotes

Author contributions: A.D.S., J.E.K., and A.H.P. designed research; A.D.S., A.H.P., and K.F. performed research; A.D.S. and J.E.K. analyzed data; and A.D.S. and J.E.K. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1713885114/-/DCSupplemental.

View Abstract

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Human presence diminishes the importance of climate in driving fire activity across the United States

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Projections of worsening wildfire conditions under climate change are a major concern in policy and management, but there is little understanding of geographical variation in fire-climate relationships. Our analysis relating climate variables to historical fire activity across the United States showed substantial variability in the importance of different seasonal temperature and precipitation variables and of climate overall in explaining fire activity.

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Climate change has inexorably stacked the deck in favor of bigger and more intense fires across the American West over the past few decades, science has incontrovertibly shown. Increasing heat, changing rain and snow patterns, shifts in plant communities, and other climate-related changes have vastly increased the likelihood that fires will start more often and burn more intensely and widely than they have in the past.

The scale and intensity of the wildfires burning across the western U.S. right now is "staggering," says Philip Higuera, a wildfire scientist and paleoecologist at the University of Montana. More than five million acres have already burned this year-and much more may be yet to come.

Noah Diffenbaugh, a climate scientist at Stanford University, makes a baseball analogy to describe increase in risk. "If there's a three-run home run in baseball, it's the home run that definitely caused the runners to round the bases and score. The home run is the proximal cause of the event. But people being on base matters," he says, and global warming is putting people on base.

Other factors also hike fire risk, like forest management decisions that have allowed for the buildup of vast amounts of vegetation that can quickly turn into fuel, as well as more problematic issues like the slow creep of houses and other infrastructure into risky areas. But for fires near that so-called wildland-urban interface, as well as more remote, forest-centered burns, climate change has significantly heightened the baseline risks.

Heat like a thirsty sponge

In some ways, fire is simple. It takes three components: the right weather and climate conditions, plenty of burnable fuel, and a spark.

"People are changing all three of those," says Jennifer Balch, a fire ecologist at the University of Colorado, Boulder. "Climate change is not the only thing going on, but it is a big and important part of the story." (Human-caused ignitions are clearly a major part of the risk: A study published in September, on which Balch was a co-author, found that humans were responsible for 97 percent of the ignitions that caused fires that then threatened homes in the wildland-urban interface, between 1992 and 2015).

Climate change has affected the first two components ( and in some cases, the third) in clear, measurable ways that have become increasingly obvious over the past few decades.

The clearest connection is with warming air temperatures. The planet has heated up nearly continuously since the start of the Industrial Revolution in the late 1800s, when humans started burning massive quantities of fossil fuels, releasing carbon dioxide that traps excess heat in the atmosphere. Since then, global average temperatures have ticked up roughly 1.8 degrees Fahrenheit (1 degree Celsius); California's change is closer to 3 degrees Fahrenheit. Warming has accelerated since the 1980s to just under 0.2 degrees Celsius (0.3 degrees F) per decade, and it's likely to accelerate further in the future.

That might not seem like very much warming, but just a little can go a long way. Hot air, if it's not at 100 percent humidity, is like a thirsty sponge: It soaks up water from whatever it touches-plants (living or dead) and soil, lakes and rivers. The hotter and drier the air, the more it sucks up, and the amount of water it can hold increases exponentially as the temperature rises; small increases in the air's heat can mean big increases in the intensity with which it pulls out water. Scientists can measure this "vapor pressure deficit"-the difference between how much water the air holds and how much it could hold. If that deficit is cranked up for a long time, soils and vegetation will parch.

A brief heat spell will dry out the smallish stuff or the already dead stuff-and maybe even some of the bigger tinder. Intense, record-breaking heat waves like the ones that encompassed the West during August and early September likely caused major crisping of burnable material, as the regional vapor pressure deficit and associated drought climbed to record levels.

"In a lot of places, you have a lot of 'flashy' fuel on the ground," says Balch. "This stuff that's as thin as paper-(like) grasses. Short-term drought events or heat waves are really impactful for drying those out." That small stuff ignites so easily that it can often help speed along a fire's spread.

When excess heat stays in place for months or longer, the wildfire risk rises even further.

An early, warm spring can jump-start a summer drought by extending the season of heat and growth, increasing the amount of water vapor that is shed by plant leaves or that evaporates directly from soil. Lower soil moisture, in turn, can feed back into the local warming cycle and intensify it, since evaporating moisture usually takes up a lot of the energy the sun beams down. When there's no moisture left to evaporate, the soil or vegetation, dead and alive, absorbs that heat instead-feeding back into the drying-out process that increases fire risk.

This year, the snow melted early; across the West, snow cover in February and March was well below its long-term average.

Then, the heat kicked in and stayed. Many western states had their hottest summers on record; the average temperature across the U.S. was 2.6 degrees Fahrenheit above the 20th-century average.

But even before that, a longer, deeper aridity had California and much of the West in its grips from 2011 until a brief period of reprieve last year. Not coincidentally, five of the state's hottest years on record occurred in the past decade.

A particularly severe phase of that persistent drought, fueled by c limate change and of an intensity not seen for the preceding 1,200 years, set in between 2012 to 2016. It stressed out the region's trees more and more as the water deficit dragged on. In the grand conifer forests of the Sierra Nevada, as in many other forests across the state, the damage accumulated.

By 2014, millions of trees had died, pushed beyond repair by the record-breaking temperatures and dryness, which reached so far into the soil that even the deep-rooted trees could find no moisture. By 2015, mass die-off was obviously underway; by 2016, the mortality count soared to about 100 million. At high elevations, nearly 80 percent of the trees died. And across the state, some 150 million trees have died since the drought's onset. Many of those trees are still there, drying out, a major fuel source ready to burn hot and bright when a fire arrives.

Since the 1970s, a recent study found, human-caused climate change caused more than half of the drying-out of burnable materials and consequent fire risk.

"These most recent heat waves are coming on top of an already hotter period, and it's all coming together and sucking moisture out of dead and live fuels, into the atmosphere," says Matthew Hurteau, a climate scientist at the University of New Mexico.

Changing rains, changing snows

Climate change is messing with the seasonal rain and snow patterns across the Western U.S., too-one of the other factors that controls fire risk.

Springtime is often coming earlier. Snowpack, which usually provides about 30 percent of the state's summer water needs, is melting earlier in year, giving the plants and soils longer to dry out. A 2016 study found that over 70 percent of the area burned in forest fires between 1970 and 2012 occurred in years where the winter snows disappeared early.

The hot drying-out season is stretching on the tail end, too, according to research published in August. Higher autumn temperatures and less precipitation-in particular, a growing delay in the onset of winter rains, which usually puts an end to the fire season in California-have led to a 20 percent increase in the number of autumn days ripe for burning.

In all, the western fire season has extended by at least 84 days since the 1970s. Cal Fire, California's fire protection service, has said publicly that it no longer considers there to be a wildfire "season," because the season is now the entire year.

The very character of the fires has also changed, growing larger and more intense, and that in turn can accelerate future fire risk. Even plants that need fire to propagate, like many high-elevation conifers, are now often finding themselves in fires more intense and powerful than they're adapted for, says Scott Stephens, a forest ecologist and fire expert at the University of California, Berkeley.

"One of the very alarming trends we're starting to see is that these fires are killing very large patches of conifers: 200, 300, 500, 1,000-acre patches, and some even larger," he says. In contrast, research from his group and others found that in the Sierra Nevada forests, before European colonizers arrived and started changing the landscape, the patches burned were small: less than an acre in many cases, or sometimes a bit bigger. And, Stephens says, the increase in fire size has accelerated in the climate-changed present, particularly since the 1990s.

That's a problem because when vast swaths of forest burn, we can no longer count on them to self-regenerate. The seed sources and gentle shade that may have been normal in the past are gone, and the conditions become ripe for highly flammable species, like non-native grasses and shrubs, to move in. Similar plant transitions are also occurring across other fire-prone habitat, like Southern California's chaparral and Colorado's forests.

So climate change has increased fire risk in both direct and indirect ways. When an ignition happens, even if it's natural- like the unusual and dramatic lightning swarm that hit the Bay Area in August-the chances of it spawning a big fire are much higher than they would be, absent climate change. Overall, over the past few decades in California, the annual average area burned increased fivefold.

Today's fires are both shocking and wholly expected, say many researchers. "That's the tricky thing about fires-it isn't any one thing that's causing them, it's multiple puzzle pieces fitting together," says Balch. Climate change. Forest management. Human behavior. Learning to adapt to the new reality and mitigate risks requires swift, decisive action from many different angles, she says.

"What this year is showing me is the nature of fires here is changing, and changing really fast," says Higuera. "We need to be doing like five things at once: patting our heads, rubbing our belly, chewing gum, and more, but for fire."

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The science connecting wildfires to climate change

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Climate change has inexorably stacked the deck in favor of bigger and more intense fires across the American West over the past few decades, science has incontrovertibly shown. Increasing heat, changing rain and snow patterns, shifts in plant communities, and other climate-related changes have vastly increased the likelihood that fires will start more often and burn more intensely and widely than they have in the past.

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Jon Keeley

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Article referenced in Salt Lake Tribune article

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Fast-Moving California Wildfires Boosted by Climate Change

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Firefighters battled nearly two dozen wildfires in California yesterday after a week of raging blazes blackened more than 1 million acres across the state. The fast-moving fires, which are seen by many scientists as a sign of climate change, have killed five people, destroyed more than 1,000 structures and forced thousands to flee.

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What do California's wildfires have to do with climate change? The connections are very strong, scientists who have studied the issue say.

While California's climate has always made the state prone to fires, the link between human-caused climate change and bigger fires is inextricable, said Park Williams, a bioclimatologist at Columbia University's Lamont-Doherty Earth Observatory. "This climate-change connection is straightforward: Warmer temperatures dry out fuels. In areas with abundant and very dry fuels, all you need is a spark," he said.

Here is a selection of our coverage of the connection between climate change and California's wildfires.

Fires in California in 2019 burned nearly 260,000 acres and researchers say record breaking years are likely to continue. As global temperatures rise, understanding fire is becoming ever more important.

Early releases of prisoners to protect them from the coronavirus have depleted the ranks of an inmate firefighting program that some say should be abolished anyway.

Related: The Incarcerated Women Who Fight California's Wildfires By choice, for less than $2 an hour, the female inmate firefighters of California work their bodies to the breaking point. Sometimes they even risk their lives.

Preparing the landscape to make future fires more manageable involves clearing fire breaks and building with more fire-resistant materials in areas of high risk. Support is also building for another method, which involves prescribed burns. It reverses the U.S. policy of suppressing fires, which has been in place for more than 100 years, and which has allowed dry fuel to accumulate. And no, the answer is not raking the forests.

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The Climate Connection to California's Wildfires

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What do California's wildfires have to do with climate change? The connections are very strong, scientists who have studied the issue say. While California's climate has always made the state prone to fires, the link between human-caused climate change and bigger fires is inextricable, said Park Williams, a bioclimatologist at Columbia University's Lamont-Doherty Earth Observatory.

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In 2001, a team of international scientists projected that during the next 100 years, the planet's inhabitants would witness higher maximum temperatures, more hot days and heat waves, an increase in the risk of forest fires and "substantially degraded air quality" in large metropolitan areas as a result of climate change.

In just the past month, nearly two decades after the third United Nations Intergovernmental Panel on Climate Change report was issued, heat records were busted across California, more than 3 million acres of land burned, and in major metropolitan areas, such as Los Angeles and San Francisco, air pollution has skyrocketed.

"This shouldn't come as a surprise to anyone," said Michael Gerrard, director of the Sabin Center for Climate Change Law at Columbia University. "Maybe we underestimated the magnitude and speed" at which these events would occur, he said, but "we've seen this long freight train barreling down on us for decades, and now the locomotive is on top of us, with no caboose in sight."

In a matter of weeks, California has experienced six of the 20 largest wildfires in modern history and toppled all-time temperature records from the desert to the coast. Millions are suffering from some of the worst air quality in years due to heat-triggered smog and fire smoke. A sooty plume has blanketed most of the West Coast, blotting out the sun and threatening people's lungs during a deadly pandemic.

California is being pushed to extremes. And the record heat, fires and pollution all have one thing in common: They were made worse by climate change. Their convergence is perhaps the strongest signal yet that the calamity climate scientists have warned of for years isn't far off in the future; it is here today and can no longer be ignored.

"What we've been seeing in California are some of the clearest events where we can say this is climate change - that climate change has clearly made this worse," said Zeke Hausfather, a climate scientist at the Breakthrough Institute, an Oakland-based think tank. "People who have lived in California for 30, 40 years are saying this is unprecedented, it has never been this hot, it has never been this smoky in all the years I've lived here."

Unprecedented, yes. But not unexpected.

Since the 1980s, government and oil industry scientists have been anticipating the events that have transpired across the state this past month.

As one 1988 internal Shell Oil Co. document noted, "by the time the global warming becomes detectable it could be too late to take effective countermeasures to reduce the effects or even to stabilize the situation."

"I'm only sorry that in 1989, I could not get an audience for what I wanted to communicate," said Jim Hansen, a retired NASA researcher and early climate change scientist, of testimony he made to Congress about the issue.

Record temperatures

Each of the extremes Californians are living through right now is fueled, at least in part, by the gradual warming of the planet, which is accelerating as greenhouse gas emissions continue to rise.

California summers are 2.5 degrees warmer than they were in the 1970s and are on track to heat up an additional 4.5 degrees by the end of the century if the world's current emissions trajectory continues, said Hausfather.

While precise attribution studies on the extreme heat waves in California in recent weeks will take time to complete, he said, they are clear examples of how climate change compounds natural weather variability to increase the likelihood of what once would have been a rare event.

"In a world without climate change, it still would have been a hot August; we still would have had some fires. But it's clear that climate change has made things notably worse," he said. "An extreme heat event that would have been 100 degrees is now 102.5 or 103 degrees, and that is actually a pretty big difference in terms of the impacts on people."

During the mid-August heat wave, Death Valley soared to 130 degrees, one of the hottest temperatures ever recorded on Earth.

Another ferocious heat wave over the Labor Day weekend brought Death Valley-like heat to other areas. Los Angeles County had its hottest temperature on record when Woodland Hills hit 121 degrees Sept. 6. At Cal Poly San Luis Obispo, it reached 120 degrees, the highest reading since record-keeping began in 1869, in an area that is less than 10 miles from the Pacific Ocean.

John Lindsey, a marine meteorologist with Pacific Gas and Electric, said the mercury rose to unprecedented levels in San Luis Obispo due to hot, downslope winds blowing from the northeast. They are known locally as Santa Lucia winds and can increase temperatures by 5.5 degrees for every 1,000 feet they descend.

"It was just rip-roaring hot," said Lindsey, who has forecast weather along the Central Coast since 1991. "You just don't expect Death Valley temperatures along coastal California."

Lindsey, who acknowledges that he was a bit of a climate skeptic in the past, said seeing the increase in seawater temperatures, in particular, over many years "was a real epiphany or wake-up call."

"By now, there's no doubt in most people's minds that the atmosphere is warming and the ocean is warming," he said. "With the way greenhouse gases are increasing, in my mind, there's no doubt that we're causing this. It's human activity that's causing this. So I'm concerned about the future. And that's somebody who's very skeptical."

Global warming has increased the odds of unprecedented heat extremes across more than 80% of the planet and "has doubled or even, in some areas, tripled the odds of record-setting hot events" in California and the Western U.S., said Stanford University climate scientist Noah Diffenbaugh.

An unprecedented firestorm

When it comes to wildfires, "what we've had in California over the last three to four weeks is unprecedented in our historical experience," Diffenbaugh said.

"This is more extreme than any other year in living memory," he said, and is consistent with the impact of global warming.

Research by Diffenbaugh and colleagues that was published last month found that the number of days with extreme wildfire weather in California has more than doubled since the early 1980s, primarily due to warming temperatures drying out vegetation.

"It means that even with no change in the frequency of strong wind events, even with no change in the frequency of lightning, the risk of wildfire and risk of large, rapidly growing wildfires goes up as a result of the effect of that warming," he said.

And it's that atmospheric warming that has set the stage for the fires raging throughout the western U.S., said Park Williams, a hydroclimatologist at Columbia University's Lamont-Doherty Earth Observatory.

"If we think of the atmosphere as a giant sponge that's always trying to extract water from the landscape, then temperature increases the sponginess," he said.

As soils become drier, heat waves become more intense. That's because the energy in the atmosphere is no longer being used in evaporation but is just building up heat. And as heat increases and soils - and, therefore, fuel for fires - dry out, the risk grows, laying the foundation for the type of wild and destructive fires we are now observing.

"That's why, I think, you keep reading quotes from these firefighters who say they are seeing fire behavior unlike anything they've seen before," he said. "As we go out in the future, in a world with this exponentially growing risk ... we're going to see fires far different than we've seen before."

He noted that fires are not unusual in California - they are an integral part of the state's history and landscape. Bad forest management, combined with human behavior - intentional and unintentional starting of fires - have contributed to the problem. But the effect of climate change is real and growing.

"We have seen the rapid warming of California summers really turbocharge the type of conditions that are suitable for rapid growth of wildfires," Hausfather said. "We see fires growing from essentially nothing to a quarter of a million acres in one day. And that's because the conditions are ripe, and temperature plays a large role."

John Abatzoglou, associate professor in the Department of Management of Complex Systems at UC Merced, agreed.

"What we are seeing play out does indeed have human fingerprints on it, including those from climate change," he said.

"We can see how warm and dry years catalyze these fires," he said, adding, however, that for fires to start, "they need to have ignitions. But the heat and dryness have absolutely set the table for widespread fire activity."
Dreadful air quality
It was no coincidence that ozone pollution levels in downtown Los Angeles spiked to their highest levels since the mid-1990s on a day in which temperatures reached an all-time high for the county, said Cesunica Ivey, an assistant professor of chemical and environmental engineering at UC Riverside who studies air quality.

The global rise in temperatures observed over decades is also occurring locally, she said, "and these frequently occurring heat waves, this upward trend in basin-wide average temperature, is contributing to ozone exacerbation."

Southern California regulators have seen decades of progress fighting smog stymied in recent years by hotter weather and stronger, more persistent inversion layers that trap pollution near the ground. Their efforts are being hindered by rising temperatures from climate change, according to air quality experts.

That's because hotter weather speeds up the photochemical reactions that turn pollutants from vehicle tailpipes and other sources into ozone, the invisible, lung-damaging gas in summer smog. Studies show that ozone levels are about two parts per billion higher than they would be without global warming.

What precisely is driving changes such as elevated smog levels can be hard to tease out in the middle of an extreme event because so much is happening at once, with multiple hazards piling on top of each other in a vicious feedback loop.

The recent heat spells, for instance, both fueled smog formation and led to power outages. Gov. Gavin Newsom suspended air quality rules on power plants and other polluters to ease strain on the grid, allowing more emissions to sully the air. The COVID-19 pandemic has added an additional layer of complexity at a time when Californians are trying to protect their homes, lungs and bodies from threats that seem to be coming from all sides.

"When you add COVID, extreme heat, wildfires and air pollution all together, they're all detrimental to public health, and it just makes things worse," said Yifang Zhu, a professor of environmental health sciences at UCLA Fielding School of Public Health who studies air pollution and its effects. "These stressors are happening at the same time. So the impact is cumulative and maybe even synergistic to each other."

That cascading effect, in which one extreme compounds another, is a feature of global warming that experts have long warned about.

Ivey, of UC Riverside, said she and other scientists aren't surprised to see so many extremes hitting simultaneously, "but to see it playing out is scary."

"It's one of those moments where ozone converged with record acres burned and a heat wave," she said. "If the writing isn't on the wall, then I don't know what to tell folks."

Global warming is also fueling increases in wildfire pollution, a mix of soot particles and gases that can fuel ozone formation and dramatically worsen smog. Those added emissions are only going to get worse as the severity and frequency of fires increases.

"People may not directly connect local air pollution to global climate change, but they are intertwined," said Zhu. "They are two sides of the same coin."

What this year's extreme heat, fire and air quality degradation is showing, said Columbia's Williams, is that we are, in a sense, blindly stepping off a cliff from a world in which we could somewhat predict what was going to happen, based on decades and centuries of data.

"We're finding that we've lost complete control," he said. "The baselines we've used for decades no longer apply. There really isn't a normal anymore."

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How climate change is fueling record-breaking California wildfires, heat and smog

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In 2001, a team of international scientists projected that during the next 100 years, the planet's inhabitants would witness higher maximum temperatures, more hot days and heat waves, an increase in the risk of forest fires and "substantially degraded air quality" in large metropolitan areas as a result of climate change.

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how climate change-driven wildfires are changing life in california - cnn

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Here's how climate change-driven wildfires are changing life in the Golden State

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Five reasons why deadlier and more destructive wildfires have become the new normal -- and they're all related to climate change.

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As Trump Again Rejects Science, Biden Calls Him a ‘Climate Arsonist’ (Published 2020)

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The president visited California after weeks of silence on its wildfires and blamed the crisis only on poor forest management, not climate change. “I don’t think science knows” what is happening, he said.

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Is climate change worsening California fires, or is it poor forest management_ Both, experts say - SFChronicle.com

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Everything you need to know about the workings of the BBC

The BBC is the world's leading public service broadcaster

We're impartial and independent, and every day we create distinctive, world-class programmes and content which inform, educate and entertain millions of people in the UK and around the world.

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Everything you need to know about the workings of the BBC

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From the section Science & Environment
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At the conclusion of UN climate talks in Madrid, our environment correspondent Matt McGrath considers the key lessons.

1. Leadership is REALLY important

COP25 in Madrid only happened because the Chilean government, faced with mounting civil disorder, decided to cancel the meeting in Santiago.

Spain stepped in and in three weeks organised a well-resourced and well-run event.

However, the fact that it was being run by one government, while hosted by another, gave rise to severe difficulties.

Delegates were highly critical of the fact that when it came to the key text about ambition, the Chileans presented the lowest common denominator language first, resulting in a huge number of objections from countries eager to see more ambition on carbon cuts.

Read full article Climate change: Five things we've learned from Madrid talks
Greta Thunberg: 'They try so desperately to silence us'
From the section Science & Environment
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Swedish activist Greta Thunberg says young people are "bringing change" to the Madrid climate talks and will not be silenced.

At a news conference Miss Thunberg said that she hoped the negotiations would yield "something concrete"

Read full article Greta Thunberg: 'They try so desperately to silence us'
Climate change: 12 years to save the planet? Make that 18 months
From the section Science & Environment
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Do you remember the good old days when we had "12 years to save the planet"?

Now it seems, there's a growing consensus that the next 18 months will be critical in dealing with the global heating crisis, among other environmental challenges.

Read full article Climate change: 12 years to save the planet? Make that 18 months
Cyclone Idai: What's the role of climate change?
From the section Science & Environment
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Unless a rich benefactor steps in, the role of human-induced climate change in Cyclone Idai is unlikely to be clearly determined.

The scientists with the expertise simply don't have the resources to do the large amount of computer modelling required.

Read full article Cyclone Idai: What's the role of climate change?
Paris climate pullout: The worst is yet to come
From the section Science & Environment
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President Trump's announcement a year ago that he was withdrawing the US from the Paris climate agreement may have been the best and worst thing that could have happened to the deal, at the same time.

"The most important piece of good news, and it wasn't a foregone conclusion, is that other countries have stayed in and doubled down on their general determination not to walk away, not to let the US 'cancel' the agreement," said former US climate envoy Todd Stern, speaking at a meeting organised by the World Resources Institute in Washington this week.

Read full article Paris climate pullout: The worst is yet to come
Trump team kicks the Clean Power Plan into the long grass
From the section Science & Environment
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In California and the western US, wildfires made more likely by climate change, continue to rage in the vineyards and forests.

In President Trump's Washington, a bonfire of climate regulations is also burning brightly.

Read full article Trump team kicks the Clean Power Plan into the long grass
Hurricanes: A perfect storm of chance and climate change?
From the section Science & Environment
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The succession of intense and deadly tropical cyclones that have barrelled across the Atlantic in recent weeks have left many people wondering if a threshold of some sort has been crossed. Is this chain of hurricanes evidence of some significant new frontier in our changing climate?

The answer is mostly no, but with worrying undertones of yes.

Read full article Hurricanes: A perfect storm of chance and climate change?
Hurricane Harvey: The link to climate change
From the section Science & Environment
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When it comes to the causes of Hurricane Harvey, climate change is not a smoking gun.

However, there are a few spent cartridge cases marked global warming in the immediate vicinity.

Read full article Hurricane Harvey: The link to climate change
The world's not laughing, Donald, it's crying
From the section Science & Environment
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President Trump's statement is a very clear repudiation of the Paris climate agreement and international efforts to fund climate mitigation and adaptation in poorer countries.

In many ways it is far worse than many observers had expected.

Read full article The world's not laughing, Donald, it's crying
Fragile future for US nuclear power
From the section Science & Environment
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No one died, there were no direct health impacts, but the Three Mile Island (TMI) nuclear accident burned so deeply into the US psyche that it has helped limit the future use of the power source across America.

A major factor in turning the accident into a "disaster" was timing. Just 12 days before the 1979 accident that saw a partial core meltdown at one of the two reactors at the Pennsylvania plant, The China Syndrome was released in cinemas across the US.

Read full article Fragile future for US nuclear power

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From the section Science & Environment Share At the conclusion of UN climate talks in Madrid, our environment correspondent Matt McGrath considers the key lessons. COP25 in Madrid only happened because the Chilean government, faced with mounting civil disorder, decided to cancel the meeting in Santiago.

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The San Francisco Chronicle is the largest newspaper in Northern California and the second largest on the West Coast.

Acquired by Hearst in 2000, the San Francisco Chronicle was founded in 1865 by Charles and Michael de Young and has been awarded six Pulitzer Prizes for journalistic excellence.

The Chronicle, available in print, online, e-edition, mobile app and iPad versions, is committed to coverage of subjects that are uniquely important to our readers: local issues and those topics with national impact such as economy, politics, technology and ecology, as well as breaking news, crime, education and national and foreign news. Readers throughout the Bay Area understand that, for coverage of the topics that matter most in their lives, the place to turn is the Chronicle and its sister site, SFGATE.

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Combined, the San Francisco Chronicle and SFGATE reach over 30 million users each month.

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The San Francisco Chronicle is the largest newspaper in Northern California and the second largest on the West Coast. Acquired by Hearst in 2000, the San Francisco Chronicle was founded in 1865 by Charles and Michael de Young and has been awarded six Pulitzer Prizes for journalistic excellence.

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The Chronicle

About this Author

J.D. Morris is a business reporter covering PG&E and local efforts to develop coronavirus treatments or vaccines.

Before joining The Chronicle, he was the Sonoma County government reporter for the Santa Rosa Press Democrat, where he was among the journalists awarded a Pulitzer Prize for their coverage of the 2017 North Bay wildfires.

He was previously the casino industry reporter for the Las Vegas Sun. Raised in Monterey County and Bakersfield, he has a bachelor's degree in rhetoric from UC Berkeley.

By This Author

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J.D. Morris, Energy Reporter, Business - San Francisco Chronicle

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The Chronicle J.D. Morris is a business reporter covering PG&E and local efforts to develop coronavirus treatments or vaccines. Before joining The Chronicle, he was the Sonoma County government reporter for the Santa Rosa Press Democrat, where he was among the journalists awarded a Pulitzer Prize for their coverage of the 2017 North Bay wildfires.

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Lee Davidson

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Lee has worked at The Tribune since 2011. He previously was a reporter for 28 years at the Deseret News, including 18 years as its Washington, D.C., correspondent. He covers politics, transportation, and demographics.

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Lee has worked at The Tribune since 2011. He previously was a reporter for 28 years at the Deseret News, including 18 years as its Washington, D.C., correspondent. He covers politics, transportation, and demographics.

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The Times attracts talented and passionate people who produce and support the distribution of the world's best news report - one that is unrivaled in its ambition, breadth and independence. All of us at the company - whether we gather news, explain why our journalism is worth paying for, defend our First Amendment rights or participate in the awe-inspiring ballet of printing and delivering the newspaper to a million doorsteps - know that the integrity of our journalism comes first.

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The Times attracts talented and passionate people who produce and support the distribution of the world's best news report - one that is unrivaled in its ambition, breadth and independence.