USA – In much of coastal southern California, the frequency of summer clouds has declined rapidly in recent decades due warming from urbanization and greenhouse gases.
These reductions have significantly reduced cloud shading and increased evaporative demand, particularly in greater Los Angeles and northern San Diego, such that a relatively cloudy summer today is similar to a relatively clear summer in the 1970s.
Clouds appear to be important regulators of summer wildfire activity in this region, as the shade they provide slows loss of moisture from vegetation.
On the vegetated mountainsides that ring coastal southern California’s large
cities, increases in summer sunlight and evaporative demand have likely enhanced summer wildfire potential over the past several decades. This effect is expected to continue due to continued urban expansion and positive feedbacks, where warming due to cloud loss promotes further warming and cloud loss.
Note: This is a simplified summary of this article. To read the original version, click HERE