California
wildfires: Why are they happening and is climate change to blame?
A cocktail
of extreme weather events is turning California’s wildfires into a deadly urban
conflagration.
By Rebecca
Ann Hughes with AP
Published on
09/01/2025 - 11:57 GMT+1
A cocktail
of extreme weather events is turning California’s wildfires into a deadly urban
conflagration.
Southern
California is experiencing its most devastating winter fires in more than four
decades.
Fires don’t
usually blaze at this time of year, but specific ingredients have come together
to defy the calendar in a fast and deadly manner.
Behind many
of them lies human-induced climate change.
Scientists
have calculated that global warming has contributed to a 172 per cent increase
in areas torched by wildfires in California since the 1970s, with a further
spread expected in the coming decades.
First are
the supersized Santa Ana winds whipping flames and embers at 100 mph (161 kmh)
- much faster than normal - crossed with the return of extreme drought.
Added to
that is weather whiplash that grew tons of plants in downpours and then the
record-high temperatures that dried them out to make easy-to-burn fuel.
Then there's
a plunging and unusual jet stream, and lots of power lines flapping in the
powerful gusts.
Experts say
that this perilous combination is what is turning wildfires into a deadly urban
conflagration.
‘The big
culprit is a warming climate’
“Tiny,
mighty and fast” fires have blazed through America's west in the last couple of
decades as the world warms, said University of Colorado fire scientist Jennifer
Balch.
She
published a study in the journal Science last October that looked at 60,000
fires since 2001 and found that the fastest-growing ones have more than doubled
in frequency since 2001 and caused far more destruction than slower, larger
blazes.
“Fires have
gotten faster,” Balch said on Wednesday. “The big culprit we're suspecting is a
warming climate that's making it easier to burn fuels when conditions are just
right.”
Summer fires
are usually bigger, but they don't burn nearly as fast. Winter fires “are much
more destructive because they happen much more quickly”, said US Geological
Survey fire scientist Jon Keeley.
AccuWeather
estimated damage from the latest fires could reach $57 billion (€55 billion),
with the private firm’s chief meteorologist, Jonathan Porter, saying “it may
become the worst wildfire in modern California history based on the number of
structures burned and economic loss”.
Winds
brought by jet stream have fanned the flames
“It's really
just the perfect alignment of everything in the atmosphere to give you this
pattern and strong wind,” said Tim Brown, director of the Western Regional
Climate Center.
Wind speed
and the speed of spreading flames are clearly linked, experts emphasise.
“The impact
increases exponentially as wind speed increases,” said fire scientist Mike
Flannigan of Thompson Rivers University in Canada.
If
firefighters can get to the flames within 10 minutes or so, its spread can be
contained, but “15 minutes, it's too late and it's gone. The horse has left the
barn”.
There's no
sure link between Santa Ana winds - gusts from the east that come down the
mountains, gain speed and hit the coast - to human-caused climate change, said
Daniel Swain, climate scientist for the California Institute for Water
Resources.
But a
condition that led to those winds is a big plunge in the temperature of the jet
stream - the river of air that moves weather systems across the globe - which
helped bring cold air to the eastern two-thirds of the nation, said University
of California Merced climate and fire scientist John Abatzoglou.
Other
scientists have preliminarily linked those jet stream plunges to climate
change.
Santa Ana
winds are happening later and later in the year, moving more from the drier
fall to the wetter winter, Keeley said. Normally, that would reduce fire
threats, but this isn't a normal time.
‘Clear link
between climate change and dry winters’
After two
soaking winters, when atmospheric rivers dumped huge amounts of water on the
region causing lots of plants to grow, a fast onset of drought dried them out,
providing perfect tinder, according to Swain and Abatzoglou.
Swain said
this weather whiplash is happening more often.
There is a
clear link between climate change and the more frequent dry falls and winters
that provide fuel for fires, Swain said.
These
devastating fires couldn't happen without the dry and hot conditions, nor would
they be blazing without the extreme wind speed, according to Abatzoglou and
others.
California's
average temperature has risen by around 1C since 1980 causing the number of
days with fire-vulnerable dry vegetation to double, fire management expert
Lindon Pronto at the European Forest Institute told Irish news site RTE.
‘Now we talk
about fire years’
An analysis
of 423 California wildfires that have grown to at least 15 square miles (39
square kilometres) since 1984 shows only four of those burned during the
winter. About two-thirds of those larger fires sparked in June, July or August.
Federal data
shows just six wildfires have burned more than 2 square miles (5 square
kilometres) in any January in California since 1984.
Until the
Palisades and Eaton fires this year, the largest had been the Viejas Fire,
which burned 17.1 square miles (44.3 square kilometres) in 2001 in the
mountains east of San Diego.
“Winter
wildfires should be an oxymoron,” University of Colorado's Balch said. “Well,
because, you know, temperatures drop and we get precipitation. We’re supposed
to get precipitation.”
Fire
officials used to talk about fire seasons, said David Acuña, a battalion chief
for Cal Fire: “Now we talk about fire years”.
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