High winds, lack of rain and climate change stoking California fires
High winds and lack of rain are the main factors driving the Southern California fires, but climate change is altering the background conditions, increasing the likelihood of these conflagrations, say experts.
Researchers have shown that a warming world increases the number of "fire weather" days, when conditions are more suited to outbreaks of fire.
California is particularly vulnerable right now because of a lack of rain in recent months, following a very warm summer.
The powerful Santa Ana winds that naturally occur at this time of year, combined with the dry conditions, can result in fast moving and dangerous fire outbreaks.
Reaching 60-70 mph, these strong, dry winds blow from the interior of Southern California towards the coast and this month has seen the worst high wind event in the area in over a decade.
The winds are drying out the lands, and researchers say that while the strongest winds will occur at the start of this outbreak, the driest vegetation will come at the end, meaning these fires could drag on for quite some time.
The high wind speeds are also altering the location of the fires. Many outbreaks occur high up on mountains, but these recent fires have rapidly moved down into the valleys and into areas where more people live.
"That's where there are more potential ignition sources," said climate researcher Daniel Swain from UCLA in a social media post.
"It's also where it's harder to turn off the power pre-emptively than it is in other locations where these public safety power shut offs are more common and are prepped for at a more regular basis. So there's going to be some potential challenges there."
The impact of a changing climate is evident in the bigger picture for the state.
California has experienced a decades-long drought that ended just two years ago. The resulting wet conditions since then have seen the rapid growth of shrubs and trees, the perfect fuel for fires.
However last summer was very hot and was followed by dry autumn and winter season - downtown Los Angeles has only received 0.16 inches of rain since October, more than 4 inches below average.
Researchers believe that a warming world is increasing the conditions that are conducive to wildland fire, including low relative humidity.
These "fire weather" days are increasing in many parts of the world, with climate change making these conditions more severe and the fire season lasting longer in many parts of the world, scientists have shown.
In California, the situation has been made worse by the topography with fires burning more intensely and moving more rapidly in steep terrain. This area of California is also dominated by naturally very fire-prone shrub vegetation.
"While fires are common and natural in this region, California has seen some of the most significant increases in the length and extremity of the fire weather season globally in recent decades, driven largely climate change," said Professor Stefan Doerr, Director of the Centre for Wildfire Research, at Swansea University.
"That said, it is too early to say to what degree climate change has made these specific fires more extreme. This will need to be evaluated in a more detailed attribution analysis."
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