Sunday, November 11, 2018

The weather and climate behind the infernos that wrecked Paradise and threaten Malibu

By Matthew Cappucci and Jason Samenow
November 9, 2018


How do these types of wildfires grow so explosively? It began with scant rainfall and abnormally warm temperatures which parched the landscape and created tinderbox conditions. Then came howling winds that fanned the flames, once the fires were sparked. And, in an environment of rising temperatures, climate change is amplifying their potential intensity.

California’s fire season typically begins in late spring, around the end of May into early June. It lasts until wintertime rains arrive in November or December, when “atmospheric rivers” carry tropical moisture into the otherwise arid region.

But this fall, hot and dry weather has persisted longer, and the rains have yet to come — fitting into a trend that is potentially expanding and intensifying wildfire season.

“[T]he fact that things are still this warm, windy, and extremely dry is becoming progressively more unusual as we head into mid-November,” tweeted Daniel Swain, a climate scientist at the University of California Los Angeles.

In an email, Swain said climate change has “shortened the rainy season at both ends and caused significant aridification [drying] of regional vegetation.”

Santa Ana winds, a seasonal breeze that can crescendo to a full-on gale, pose a serious danger when it’s this dry.


The warming climate only makes a hot, dry weather pattern — prone to fire-fanning winds — more extreme. It intensifies a process known as evapotranspiration in which plants release water into the air. The warmer the air, the more water plants release.

These warmer temperatures translate to the vegetation drying up, littering the ground as crisp, brittle plant matter ripe for fueling a blaze. The soil is also starved of moisture, offering little protection against the spread of fires.

“[L]ocal vegetation was at record dry levels for the time of year when the fire started, and that is part of the reason why this event ultimately became as bad as it did,” Swain said.

California is warming — fast. Faster than many other states.

The January through October period ranked as the fourth-warmest on record. The five warmest years on record have all occurred in the last five years.


Los Angeles has warmed 3.2 degrees since the 1940s. Farther north, the increase has been even more noteworthy.

As temperatures have warmed, precipitation has remained steady or decreased, further drying out vegetation in many cases.

With the onset of hot, dry conditions coming sooner and wintertime precipitation falling in shorter but more intense bursts, the stage is set for routine drought during the summer months.

Last year, the U.S. Department of Agriculture announced that a record 129 million trees — “mostly conifers” — died as a result of drought. The agency cited an “increased wildfire threat” for 2018 in its December 2017 report, adding that 56 percent of its national budget was consumed by firefighting efforts.

Going into the 2018 fire season, experts already knew it would be bad. The 129 million dead trees covered a historic 8.9 million acres, the department said.

But the last piece of the puzzle? Where we build. Irrespective of climate change, wildfires will inevitably claim more structures if we continue to build and expand their targets.


Gabrielle Canon in Los Angeles
Sun 11 Nov 2018 15.50 EST

Fire chief: climate change helped make California wildfires more devastating


As Los Angeles fire chief Daryl Osby took the podium, strong gusts swirled smoke, ash and dust through grey skies. Along with updates on progress in fighting the fire, he said this blaze signified a shift: fire crews are now facing the most erratic and challenging fight of their lives.

Climate change, Osby said, was undeniably a part of why the fires burning in northern and southern California were more devastating and destructive than in years past.

The death toll stood at 25: two in the LA-area fires, 23 around the destroyed town of Paradise 500 miles to the north. The total was expected to rise.

“The fact of the matter is if you look at the state of California, climate challenge is happening statewide,” Osby said, adding that “it is going to be here for the foreseeable future”.


Drought conditions have increasingly affected the state over the past decade, causing erratic fire behavior and making efforts to contain the flames much more difficult. The Woolsey fire, which was only 10% contained on Sunday, has burned more than 87,000 acres in three days. More than 177 homes have been lost and officials said that number was expected to rise rapidly.

The fire season, which started in early summer, is poised to break records for a second year in a row. In July California’s outgoing governor, Jerry Brown, referred to megafires as the “new normal”.

After the press conference, Osby told the Guardian environmental changes had expanded fire season across the state. Crucially, this has put a crunch on resources. For an immediate example, the Camp fire in the north, which devastated Paradise, has diverted resources that drier areas of southern California could once rely on for backup.

“It did have an affect on our strategy,” he said. “Typically we would rely on our partners to the north to come. But they are fighting a major fire up there.”

Southern California fire crews therefore only had capacity to focus on saving lives and structures as the fire moved and were unable to work on containing the flames for three days.


“What really hampered our ability to combat this fire is we didn’t have enough resources for containment,” he said. “Normally we would do all three things simultaneously but now we have to do it in sequential order. Lives are first.”

tags: severe weather, extreme weather

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