Explained: Why this is the worst wildfire season in western US

29 October 2020

Published by https://indianexpress.com/

USA – Fast-moving wildfires in southern California have seriously injured two firefighters as of Monday, and forced over 100,000 people to evacuate in what has been referred to as the worst wildfire season the state has seen on record.

Out of the six largest wildfires in California recorded since 1932, five occurred in 2020. The largest out of these were in August, called the August Complex fires, and burned an area of about 1,032,264 acres, resulting in one death. This year has also seen the most destructive and deadliest wildfires, with the North Complex wildfire coming at number five in both the categories since the records have been maintained.

The fires caused the skies around the San Francisco Bay area and in some parts of Oregon and Washington to turn orange as a result of the smoke and ash, and also affected the air quality in these areas.

Wildfire season in California 

Typically, wildfire season in the western US stretches from late spring until seasonal winter rains and snow arrive. Further, around the world, wildfires or forest fires occur during hot and dry seasons. Since dry leaves, shrubs, grass and deadwood are easily combustible, they are easy to ignite. Ignition can either happen naturally such as from lightning strikes, or can be triggered accidentally, such as from cigarette stubs.

Sometimes, however, ignition can be intentional, such as to clear the land or to control an incoming forest fire by removing vegetation that would provide more fuel to it. Such fires typically come to an end when there is no more vegetation to burn or because of rain.

How did the California wildfires start this year?

NASA’s Earth Observatory has noted that wildfires were ignited in California in August after an “unprecedented outburst of dry lightning”. This year has also recorded at least ten lightning complex fires. One reason could be that climate change is leading to more lightning storms.

But there are other ways by which wildfires can be ignited. As per The New York Times, most wildfires in California are caused by people. The El Dorado fires for instance, that have been mostly contained now, were ignited after a family used a “pyrotechnic device” to announce the gender of their new baby, the report mentions.

Other reasons include power transmission lines or other utility equipment that can ignite fires in remote areas. Once fires are started, they are made worse by strong, dry winds.

According to a paper published in the journal Proceedings of the National Academy of Sciences in 2017, humans are responsible for 84 per cent of the wildfires. The co-author of this paper Jennifer Balch told Science magazine in an interview the same year that in the US, of the 1.5 million wildfires on record, 25 per cent were started due to the burning of trash and debris, about 22 per cent were started due to unknown human causes and the next biggest reason for wildfires includes arson, followed by heavy equipment, campfires, children and smokers.

Why are they especially deadly this year?

As per the California Department of Forestry and Fire Protection (CAL FIRE), while wildfires are a natural part of the state’s landscape, the fire season in the state and across the Western US is starting earlier and ending later each year.

The department notes that climate change is a “key driver” of this trend, with warmer spring and summer temperatures, reduced snowpack and earlier spring snowmelt, which create longer and more intense dry seasons. These dry seasons have increased the moisture stress on vegetation and have therefore made forests more susceptible to severe wildfires.

According to CAL FIRE, from January 1-October 25 this year, there have been more than 8,800 wildfires in the state that have burned an area of more than 4 million acres. The fires have led to 31 fatalities and have damaged or destroyed more than 10,000 structures. A combination of record high temperatures, strong winds and greater number of lightning storms could be contributing to the severity of the current wildfire season in California.

The Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), which was published in 2013, identified a few factors that could influence the way wildfires play out. These include a global increase in average temperatures, global increases in the frequency, intensity and extent of heatwaves (breaching of historically extreme temperature thresholds) and regional increases in the frequency, duration and intensity of droughts.

So, is climate change entirely to blame?

Scientists are wary of attributing any single contemporary event to climate change, mainly because of the difficulty in completely ruling out the possibility of the event having been caused by some other reason, or a result of natural variability.

In an analysis of scientific articles published since January 2020 that established a link between climate change and fire risk, the authors note that natural variability is superimposed on the increasingly warm and dry conditions that have resulted from climate change, which has led to more extreme fires and more extreme fire seasons.

The New York Times has noted fire suppression, strong gusts of winds called the Santa Ana wind and the possibility of people igniting fires as reasons other than climate change that are making wildfires in California especially catastrophic.

What’s the situation right now?

According to CAL FIRE, due to strong winds across much of California, firefighters are on high alert, while Red Flag warnings are in effect throughout much of the state due to extreme fire weather conditions.

At the moment, the Silverado fire, that is spread over 7200 acres, and the Blue Ridge fire, spread over 3,000 acres, are some of the largest fires in the state. Both have been contained zero per cent as of Monday. The current situation in southern California is probably due to an onslaught of extreme winds and low humidity levels.

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