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.
Since 1880, the world has warmed by 1.9 degrees Fahrenheit (1.09 degrees Celsius), 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, and 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 devasting 2017 fire season. In 2019, wildfires have already burned 2.5 million acres in Alaska in an extreme fire season driven by high temperatures, which have also led to massive fires in Siberia.
“Our ability to track fires in a concerted way over the last 20 years with satellite data has captured large-scale trends, such as increased fire activity, consistent with a warming climate in places like the western U.S., Canada and other parts of Northern Hemisphere forests where fuels are abundant,” said Doug Morton, chief of the Biospheric Sciences Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Where warming and drying climate has increased the risk of fires, we’ve seen an increase in burning.”