Monday, November 26, 2018

How climate change is fueling California’s record wildfires

By Dana Nuccitelli


climate scientists have found that global warming is impacting us now. It’s making extreme weather like droughts, floods, heat waves, and wildfires worse. It’s important to be able to communicate the science to people to help them understand that climate change is a much higher priority. The scientific evidence connecting climate change to California’s horrific wildfires presents one such opportunity


There are four primary ways climate change worsens these fires:

Higher temperatures dry out vegetation and soil, creating more wildfire fuel.
Climate change is shortening the California rainy season, thus extending the fire season.
Climate change is also shifting the Santa Ana winds that fan particularly dangerous wildfires in Southern California.
The warming atmosphere is slowing the jet stream, leading to more California heat waves and high-pressure ridges in the Pacific. Those ridges deflect from the state some storms that would otherwise bring much-needed moisture to slow the spread of fires.


To paraphrase the cliché, what happens in the Arctic doesn’t stay in the Arctic. The Northern Hemisphere jet stream is a result of the temperature difference between the cold Arctic and warmer lower latitudes in regions like North America and Europe. But the Arctic is the fastest-warming region on Earth, largely because as reflective sea ice disappears, the Arctic surface is increasingly covered by dark oceans that absorb more sunlight. The rapidly warming Arctic is shrinking the temperature difference between that region and the lower latitudes, which in turn weakens the jet stream. As a result, rather than a fast-moving flow of air, the jet stream increasingly is taking a slow, meandering path across the Northern Hemisphere.

Weather patterns tend to get stuck between those jet stream waves and “stall” in place. This can make a storm or hurricane dump a lot of rain in one spot; or a heat wave or cold polar air persist in a given region; or in California’s case, high-pressure ridges tend to stall off the coast in the Pacific Ocean.

These high-pressure systems tend to divert storm systems to the north of California, exacerbating dry conditions. This often happened during California’s 2012–2016 drought – the state’s worst in over a millennium – and another such ridge has been sitting of California’s coast in 2018:


in an October 2018 paper in Science Advances, scientists Michael Mann and Stefan Rahmstorf and colleagues found that depending on how human fossil fuel pollution changes in the coming years, the frequency of wavy jet stream events could triple by the end of the century.


A 2015 special report in the Bulletin of the American Meteorological Society found that “An increase in fire risk in California is attributable to human-induced climate change.” And a 2016 study in the Proceedings of the National Academy of Sciences found that human-caused global warming doubled the area burned by wildfires in the western U.S. over just the past 30 years.

The reality is that the more global warming humanity causes, the worse California’s wildfires will become.

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