High winds and lack of rain are major factors driving Southern California wildfires, but climate change is changing background conditions, making these fires more likely, experts say.
Researchers have shown that a warming world increases the number of “fire weather” days, when conditions are more suitable for fires to break out.
California is particularly vulnerable right now due to the lack of rain in recent months, after a very warm summer.
The strong Santa Ana winds that naturally occur this time of year, combined with dry conditions, can spark fast-moving and dangerous fires.
Reaching speeds of up to 60-70 mph, these strong, dry winds blow from inland Southern California toward the coast, and this month has seen the region's worst high wind event in more than a decade.
Winds dry out lands, and researchers say that while the strongest winds will occur at the beginning of this outbreak, drier vegetation will come in eventually, meaning these fires may persist for some time.
High wind speeds also change the location of fires. Many outbreaks occur high in the mountains, but these recent fires have moved quickly into valleys and areas where more people live.
“This is where there are more potential ignition sources,” Daniel Swain, a climate researcher from the University of California, Los Angeles, said in a social media post.
“It's also a place where it's harder to turn off power proactively than it is in other locations where public safety power shutoffs are more common and prepared for on a more regular basis. So there will be some potential challenges there.”
The impact of climate change is evident in the country's bigger picture.
California experienced a decades-long drought that ended just two years ago. The resulting wet conditions have since seen rapid growth of shrubs and trees, ideal fuel for fires.
However, last summer was very hot, followed by a dry fall and winter, and downtown Los Angeles has received only 0.16 inches of rain since October, more than 4 inches below average.
Researchers believe that a warming world is increasing the conditions that lead to wildland fires, including lower relative humidity.
Scientists have shown that “fire weather” days are increasing in many parts of the world, as climate change makes these conditions more dangerous and the fire season lasts longer in many parts of the world.
In California, the situation was exacerbated by the terrain, where fires burned more intensely and moved more quickly in steep terrain. This area of California is also dominated by shrub vegetation that is naturally vulnerable to fire.
“Although fires are common and natural in this region, California has seen some of the most significant increases in fire season length globally in recent decades, largely driven by climate change,” said Professor Stefan Doerr, director of the center. for Wildfire Research, at Swansea University.
“However, it is too early to determine the extent to which climate change has made these specific fires more dangerous. This will need to be assessed through a more detailed attribution analysis.”
