Wednesday, January 29, 2025

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Conditions that fueled L.A. fires were more likely due to climate change, scientists find

Evan Bush
NBC
January 28, 2025 


A firefighter battles the Palisades Fire while it burns homes in Los Angeles on Jan. 8.

Climate change increased the likelihood of the extreme conditions that allowed the recent fires to roar across the Los Angeles area, an international group of scientists said Tuesday.

The hot, dry and windy conditions that preceded the fires were about 35% more likely because of human-caused global warming, according to a new report from the World Weather Attribution group, which analyzes the influence of global warming on extreme events.

The fires, which started during a ferocious windstorm and after almost no rain had fallen in greater Los Angeles since the spring, have killed at least 29 people and torched more than 16,000 buildings, including homes, stores and schools.

“This was a perfect storm when it comes to conditions for fire disasters — the ingredients in terms of the climate enabling, the weather driving the fires and the huge built environment right downwind from where these ignitions occurred,” John Abatzoglou, a professor of climatology at the University of California, Merced, who contributed to the report, said at a news conference.

Compared to a preindustrial time before fossil fuels were widely used, there are now 23 extra days of “dry season” on average each year in the Los Angeles region, the report said, making it more likely that fires will coincide with seasonal Santa Ana winds.

Park Williams, a professor of geography at UCLA and an author of the report, said fires during cool seasons in Southern California require four conditions: widespread grass or brush that can burn, abnormally dry conditions, an ignition (which almost always comes from a person; and extreme weather, like the recent windstorm. He described each of those conditions as an individual switch in a system that requires all four to be flipped on for light to emanate.

“The artificial warming due to human-caused climate change is making the light brighter,” Williams said.

The authors of the report analyzed weather and climate models to evaluate how a warmer atmosphere is shifting the likelihood of fire weather (meaning conditions that increase the risk of wildfire). They also tracked how a metric called the Fire Weather Index changed over time. The index tracks temperature, relative humidity and wind speeds, all factors that contribute to the likelihood of fire.

The researchers found that the kind of conditions that drove the L.A. area fires are expected to occur on average once in 17 years in today’s climate. Such conditions would have been expected once every 23 years without climate change and would have been less extreme when they did occur, the report says.


Homes destroyed in the Palisades Fire in Los Angeles.

As a group, World Weather Attribution is a loose consortium of scientists who publish rapid findings about climate change’s role in extreme weather events. Although their research methods are peer-reviewed, this specific rapid analysis has not been through the rigor of a typical academic review process, which can take months or longer. The group’s prior analyses of heat, wildfire and hurricane disasters have held up to scrutiny after initial release and were ultimately published in academic journals.

For climate attribution scientists studying how much climate change is to blame for specific events, wildfire disasters are notoriously challenging to untangle, and local nuances are extremely important.

In the case of the recent California fires, the report's authors found that although climate change played a role, it was not the sole factor.

The hillsides surrounding Los Angeles are filled with brush that has evolved to burn with regularity, and more people are in these areas today than in the past to potentially start fires via cigarettes, power lines, fireworks, vehicles or other sources. Additionally, neighborhood development has pushed deep into areas prone to burn, which means houses are serving as fuel for wildfires and contributing to its rapid spread.

“Fire in Southern California is highly complex, right? It’s a combination of a number of things. This is a landscape that’s got a really distinct human imprint on it,” Abatzoglou said, adding that the Los Angeles region has “a large population, a lot of ignitions, a lot of land-use related issues.”

The influence of climate change on the Santa Ana winds, one of the driving factors behind the Los Angeles fires, remains murky. The report's authors said that some research suggests the winds will become less intense as the climate warms; however, other research suggests this wind pattern will persist and perhaps intensify during the cold months.




“We don’t know of a direct mechanism that would link climate change to the winds, but there could be," Williams said. "We just don’t know."

This article was originally published on NBCNews.com


Climate change made LA fires worse, scientists say

Matt McGrath 
BBC- Environment correspondent
Wed, January 29, 2025 


[Getty Images]


It made those weather conditions about 35% more likely, according to World Weather Attribution - globally recognised for their studies linking extreme weather to climate change.

The authors noted that the LA wildfire season is getting longer while the rains that normally put out the blazes have reduced.

The scientists highlight that these wildfires are highly complex with multiple factors playing a role, but they are confident that a warming climate is making LA more prone to intense fire events.

"Climate change increased the risk of the devastating LA wildfires," said Dr Clair Barnes, from Imperial College London, the study's lead author.

"Drought conditions are more frequently pushing into winter, increasing the chance a fire will break out during strong Santa Ana winds that can turn small ignitions into deadly infernos."

The Santa Ana winds are strong and gusty east or north-easterly winds that blow from inland California towards the coast.

Around 30 people have died and more than 10,000 homes have been destroyed in the fast-spreading, destructive fires that broke out in early January.

This new study looks at what are termed the fire-prone conditions that can lead to dangerous conflagrations.

It's been carried out by a team of researchers from World Weather Attribution (WWA), a global group that publishes rapid analyses of climate-related weather events.

They use climate models to simulate how the warming that has occurred since the middle of the 19th century is influencing heatwaves, droughts, floods and fires.

The widespread burning of coal, oil and gas in the wake of the industrial revolution has driven billions of tonnes of planet-warming gases into the atmosphere.


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Acting like a blanket, these gases have driven up temperatures by around 1.2C since then.

By using climate models and statistical methods along with real world observations, the WWA group have been able to show how much of an influence climate warming has had on extreme events.

In the case of the LA fires, they found that the hot, dry conditions that drove them are expected to occur once every 17 years.

This is an increase in likelihood of around 35% compared to a world that hadn't experienced warming.

"We actually see that the models show very much the same results that the [real world] observations have," said Dr Friederike Otto, the head of World Weather Attribution.


"So there, in this combined index, we are quite confident about the result... we have actually a signal that we can say that we definitely can attribute that, also quantitatively."

The researchers also examined other important variables that can lead to wildfire including the length of the fire season.

By analysing weather observations, the scientists found that this has increased by around 23 days since the world began warming, around 1850.

The team say that this means the dry conditions and the Santa Ana winds that are crucial for the spread of fires, are increasingly overlapping.


[Getty Images]

Another key element is drought.

Dry conditions in the LA area over the October to December period are now about 2.4 times more likely than before humans starting using fossil fuels on a large scale.

The researchers are clear that climate change increased the probability of the hot, dry conditions that gave rise to the fires.

However, the authors are more cautious about the link between rising temperatures and the longer fire season or decreased rainfall, saying that the models did not show a significant connection.

Despite these reservations, the conclusion is that a warmer world increased the chances of the devastating wildfires occurring - as more fossil fuels continue to be burnt, those chances will continue to rise.

"Overall the paper finds that climate change has made the Los Angeles fires more likely despite some statistical uncertainty," said Prof Gabi Hegerl, from the University of Edinburgh, who was not part of the study team.

"This is a carefully researched result that should be taken seriously," she said in a statement.


[Getty Images]

The new work builds on research that was published while the fires were still burning fiercely.

That study linked the wildfires to what's termed "climate whiplash."

The idea is that very wet years are followed almost immediately by very dry ones, which increases the risk of fires.

This is what happened in LA, when two wet winters were followed by an extremely dry autumn and winter this year – the wet weather promoted the growth of grass and shrubs that became the fuel for the fires that took off in the gusting Santa Ana winds.

[BBC]

L.A. fire conditions made 35 per cent more likely thanks to climate change, researchers say

CBC
Tue, January 28, 2025

A firefighter hoses down flames as the Palisades Fire approaches in Mandeville Canyon, Jan. 11 in Los Angeles. Researchers say the conditions behind the fires were about 35 per cent more likely compared to pre-industrial times. 
(Jae C. Hong/The Associated Press - image credit)


The fires that devastated neighbourhoods in Los Angeles, killing 28 people and burning over 16,000 homes and buildings are not a one-off, according to a new rapid analysis. And researchers say they are now significantly more likely to happen due to climate change.

The shocking scenes of fires lapping up city blocks in North America's third largest metropolis are driving home just how close the climate crisis is bringing extreme weather to people and communities. The new study, from the World Weather Attribution (WWA) group, says the conditions behind the fires were about 35 per cent more likely compared to pre-industrial times.

If global warming continues along current trajectories, the fire conditions will be another 35 per cent more likely by the year 2100 — painting a bleak picture for the future of L.A. and southern California.


"Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier and more flammable," said Clair Barnes, a co-author of the WWA report and researcher at Imperial College London.

The study, carried out by an international team of 32 researchers, used global climate models to project how weather conditions driving the fires have changed since pre-industrial times. To be published quickly, the study has not been peer-reviewed or been published in a scientific journal, but is based on established attribution methods.

These conditions are now expected to happen once every 17 years, although they will happen more frequently as global temperatures continue to rise.

Put more simply, climate change delayed rains and intensified the hot and dry conditions that turned the vegetation around L.A. into fuel, and then strong winds made those fires go where they normally don't. All this will become more likely as global temperatures keep rising.


The devastation from the Palisades Fire is shown in an aerial view in the Pacific Palisades neighborhood of Los Angeles on Jan. 27, 2025.
 (Jae C. Hong/The Associated Press)

Delayed winter rain extends fire season

"The delayed onset of winter rains is a significant problem because it ends up extending the length of the fire season, which means that there's that many more opportunities for weather events like these wind events to align with ignitions," said John Abatzoglou, a professor of climatology at the University of California Merced and one of the study co-authors.

He noted that when all of these things line up, there's a greater risk that one of the resulting fires becomes "very difficult to suppress."

The dry conditions also came after a couple years where California saw more rain, which led to more vegetation growing in the area. Abatzoglou says that means even more fuel is available to burn, allowing the fire to spread.

And the underlying conditions are all set to get worse. Low rainfall from October to December is now 2.4 times more likely, according to the WWA report, driving up the risk of dry, fire-prone vegetation. It also means that the dry conditions are coinciding more closely with the strong Santa Ana winds, which helped spread these fires and generally peak between December and January.


John Borbone searches through his fire-ravaged property after the Palisades Fire in the Pacific Palisades neighbourhood of Los Angeles. (Jae C. Hong/The Associated Press)

In total the dry, fire-prone conditions in southern California have extended by about 23 days every year, increasing the risk to cities like L.A., according to the study.

Abatzoglou says he hopes that the destructive fires will act as a wake-up call for the state to be prepared to face these conditions the next time they happen.

"Because there will be a next time."



Climate change made the deadly Los Angeles wildfires more likely. And, the worst is yet to come

Julia Musto
Tue, January 28, 2025 


Firefighters battle the Kenneth fire in the West Hills section of Los Angeles earlier this month. The state’s deadly wildfires were made worse due to impacts from climate change, scientists said Tuesday (AP)

The devastating wildfires that resulted in the deaths of 29 Californians this month were made more likely due to the impact of climate change, researchers said Tuesday.

The blazes were worsened by dried-out vegetation, low rainfall in the region and the overlap between drought conditions and hurricane-force Santa Ana winds, according to the group World Weather Attribution.

“Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier, and more flammable,” Dr. Clair Barnes, a researcher at England’s Imperial College London, said in a statement.

The international research published Tuesday found that the hot and dry conditions that drove the recent fires were about 35 percent more likely due to warming caused primarily by the burning of oil, gas and coal that releases atmosphere-warming greenhouse gases.

These tinderbox conditions will become 35 percent more likely with 2.6 degrees Celsius (4.7 degrees Fahrenheit) of global warming relative to preindustrial levels. Under recent pledges to take climate change, a United Nations report found that temperatures would still rise by that much or more by the year 2100.

After months without rain, Southern California finally saw downpours and snow this week. But, low rainfall between the months of October and December, the study said, is now about 2.4 times more likely compared to the preindustrial climate.

In addition, hotter temperatures are evaporating more moisture from plants, making them easier to burn.

“All the pieces were in place for a wildfire disaster – low rainfall, a build-up of tinder-dry vegetation, and strong winds,” Park Williams, a professor of geography at UCLA, explained.


Plumes of smoke from the Hughes fire rise last week in Castaic, California. The fires are largely contained now, after weeks of intense efforts to fight flames amid critical fire weather (AP)

To determine how climate change may have played a role in promoting the late-year fire weather, researchers combined weather data with climate models.

But the models did not perform well due partially to the small and mountainous study area and sparse rainfall, World Weather Attribution noted. They indicated that there was an influence on hot, dry and windy conditions, but did not show a significant impact on rainfall on the fire season’s end date.

Still, scientists said they were confident that climate change is an important driver of the changes, citing existing research and real-world data.

“In 2025, the choices facing world leaders remain the same – to drill and continue to burn oil, gas and coal and experience ever more dangerous weather, or transition to renewable energy for a safer and fairer world,” Dr. Friederike Otto, World Weather Attribution’s co-lead and Senior Lecturer in Climate Science at Imperial College London, said.





Climate change primed LA to burn — catastrophically
Matt Simon
Tue, January 28, 2025 



From the first reports of wildfires breaking out around Los Angeles earlier this month, scientists could say that climate change had worsened the blazes. Sure, wildfires would burn in California regardless of planetary warming, but extra-dry fuels had turned the landscape into tinder. The resulting blazes, fanned by 100-mile-per-hour Santa Ana wind gusts, burned 50,000 acres. They killed at least 28 people and destroyed more than 16,000 structures, causing perhaps hundreds of billions of dollars of damage and economic losses.

A more thorough analysis published Tuesday found that those extremely dry and hot conditions were about 35 percent more likely thanks to climate change. Rains starting in October normally dampen the Southern California landscape, reducing wildfire risk, but the almost nonexistent rainfall this autumn and winter was about 2.4 times more likely when compared to a preindustrial climate, according to the study by World Weather Attribution, a U.K.-based research group. The region now has 23 additional days of fire-prone conditions each year, the analysis found, meaning more opportunities for blazes to spread out of control.

“Drought conditions are more frequently pushing into winter, increasing the chance a fire will break out during strong Santa Ana winds that can turn small ignitions into deadly infernos,” said Clair Barnes, a World Weather Attribution researcher at Imperial College London’s Centre for Environmental Policy, in a statement. “Without a faster transition away from planet-heating fossil fuels, California will continue to get hotter, drier, and more flammable.”

A major driver of these catastrophic wildfires is “weather whiplash,” the report notes. Wet seasons are getting wetter, a result of a hotter atmosphere being able to hold more moisture, while dry seasons are getting drier. In the two previous winters, Los Angeles got significant rainfall, leading to the explosive growth of grasses and shrubs. But then an atmospheric switch flipped, and the metropolis got almost no rainfall between May 2024 and this January, so all that extra vegetation dried out. “Very wet years with lush vegetation growth are increasingly likely to be followed by drought, so dry fuel for wildfires can become more abundant as the climate warms,” said Theo Keeping, a wildfire researcher at Imperial College London’s Leverhulme Centre for Wildfires and co-author of the report, in the statement.

In a separate analysis released on January 13, researchers at the University of California, Los Angeles, found that climate change could be blamed for roughly a quarter of the dryness of the vegetation that burned in the fires, which they described as a conservative estimate. The study also found that the region’s weather whiplash set the stage for disaster. “Under a warmer climate, you also have what people would call a ‘thirstier’ atmosphere trying to draw up as much moisture as it can,” said Chad Thackeray, a climate scientist at UCLA and co-author of the report.

And then came the seasonal Santa Ana winds at the start of January, which blew strong and dry. In a matter of hours or even minutes, that air can desiccate the vegetation further still. All it took was sparks for several wildfires to rapidly spread. The Santa Ana winds not only shoved those fires along with breathtaking speed, but also created unpredictable swirls that made the blazes behave erratically. That made the wildfires exceedingly difficult to fight — especially for crews already spread thin fighting on multiple fronts, as the disabled and elderly in particular struggled to evacuate in time. “Realistically, this was a perfect storm when it comes to conditions for fire disasters,” said John Abatzoglou, a climatologist at the University of California, Merced, and co-author of the World Weather Attribution report, on a press call Tuesday morning.

And conditions in Southern California will probably get worse from here. The World Weather Attribution analysis estimates that fire-prone conditions in the region will become 35 percent more likely still if the world warms by 2.6 degrees Celsius above preindustrial levels.

For as much as climate change influenced the Los Angeles wildfires, a few factors operate separately. For one, climate change doesn’t create Santa Ana winds. And scientists don’t expect Santa Ana winds to get stronger as the planet warms — they might even get slightly weaker — though that will require more research to fully tease out. And two, humans spark the vast majority of wildfires in California, be it with electrical lines, fireworks, or arson. And lastly, developers keep building homes in the densely vegetated “wildland urban interface,” where the risk of wildfire is extreme.

This growing risk presents a daunting challenge for communities as they rebuild. Homeowners, for instance, have to keep their yards clear of vegetation and adopt fire-proof building materials, which gets expensive. “Communities can’t build back the same because it will only be a matter of years before these burned areas are vegetated again and a high potential for fast-moving fire returns to these landscapes,” said Park Williams, a geographer at UCLA and co-author of the World Weather Attribution report, in the statement.

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