NASA’s Earth Science News

Hot and dry. These are the watchwords for large fires. While every fire needs a spark to ignite and fuel to burn, the hot and dry conditions in the atmosphere determine the likelihood of a fire starting, its intensity and the speed at which it spreads. Over the past several decades, as the world has increasingly warmed, so has its potential to burn. Lately it’s Australia.

Since 1880, the world has warmed by 1.9 degrees Fahrenheit (1.09 degrees Celsius). All with the five warmest years on record occurring in the last five years.

Since the 1980s, the wildfire season has lengthened across a quarter of the world’s vegetated surface. Then in some places like California, fire has become nearly a year-round risk.

The year 2018 was California’s worst wildfire season on record, on the heels of a devastating 2017 fire season. In 2019, wildfires have already burned 2.5 million acres in Alaska.

That’s in an extreme fire season driven by high temperatures. All which have also led to massive fires in Siberia.

Whether started naturally or by people, fires worldwide and the resulting smoke emissions and burned areas have been observed by NASA satellites from space for two decades. Combined with data collected and analyzed by scientists and forest managers on the ground, researchers at NASA, other U.S. agencies and universities are beginning to draw into focus the interplay between fires, climate and humans.

As Yale Climate Connections reporting that with global temperatures rising comes more wildfires. Also they are getting more frequent and intense.

Wildfire

Across the United States and around the world, wildfires are growing. Especially in intensity and frequency. Wildfire season can spark anytime throughout the year in arid regions where Mediterranean climates predominate.

That’s such as Spain, Portugal, and much of California as reported in October 2019 by National Geographic.

That dry, wooded regions where people and wild lands exist in close proximity have grown especially dangerous. So as rural communities become trapped by rapidly spreading conflagrations.

Climate scientists have correlated the growing incidence and intensity of wildfires with rising global temperatures. Few places seem immune: Australia; Indonesia; Canada; Alaska; the American northwest, southwest and southeast; Chile; and Western Europe have all seen massive and destructive wildfires in recent years. In federally managed forests in the western U.S. today, wildfires larger than 1,000 acres have become nearly five times more frequent and burned areas 10 times as large as in the 1970s, according to research by LeRoy Westerling at the University of California at Merced. This time period corresponds to significant warming documented around the globe: Two-thirds of the 1.4-degree rise in average global temperatures since 1880 has occurred since 1975, according to NASA’s Earth Observatory.

How climate change affects wildfires

Climate change contributes to more and bigger wildfires in a variety of ways.

The rise in average global temperatures has led to higher spring and summer temperatures, and importantly an earlier onset of spring. This pattern has led to a rapid melting of spring snowpack, causing soils to dry out earlier and remain dry longer.

After months of drying in the longer periods of higher temperatures, stressed forests have become more susceptible to infestations by bark beetles and other insects that thrive in warmer temperatures. Throughout the western United States and Canada, bark beetles have killed off hundreds of millions of trees and devastated forestlands, turning them into kindling for catastrophic wildfires. Insect outbreaks killed more than 300 million trees in Texas in 2011, and more than 129 million trees in California from 2010 to 2017, according to the Fourth National Climate Assessment, released in 2018.

Warming temperatures have allowed populations of mountain pine beetles to explode at elevations and latitudes where winters were historically cold enough to limit their numbers. These insects have killed trees across more than 25 million acres in the western U.S. since 2010. In California, the level of tree mortality has been so high in some areas that 70 percent of trees died in a single year.

In conclusion and meanwhile, the West Coast of the U.S. is particularly susceptible to a kind of weather whiplash. All wet winters fueled by atmospheric river storms originating in the Eastern Pacific. Then followed by parched summers that dry out spring vegetation. Then to transform it into kindling for wildfires in the fall. A 2018 study in Nature Climate Change projected a 25 percent to 100 percent increase. Finally and in extreme dry-to-wet precipitation events.

By Bruce Lieberman on Jul 2, 2019

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