Since the middle of August 2020, hundreds of wildfires have been burning in California, from near the Mexico border to the forests of the Sierra Nevada. Record-high temperatures in addition of strong winds further energized the flames, prompting the fires to spread rapidly and sending plumes of ash and smoke into the skies across several states. A satellite image taken Monday showed smoke blowing as far east as Kansas.
Historically, fire season in California peaks in October during drought peak. But as temperatures rise, extreme drought conditions will occur earlier in the year. Average temperatures statewide rose by 1.8°C since 1980, while precipitation dropped by 30%. That doubled the number of autumn days that offer extreme conditions for the ignition of wildfires. Climate models estimate that average state temperatures will climb by 2 to 3°C by 2050.
Hotter temperatures, reduced summer precipitation and snow that melts sooner in spring lead to drier soils and parched vegetation. Surrounded by warm air, the plants lose additional moisture. The dry vegetation can easily be ignited by lightning strikes or open fire, and provides abundant fuel to the flames.
Esri – a California based software company specialized in data visualization and maps – recently created a short video that maps the location and size of wildfires in California from 1910 to 2019. As the video shows, wildfires are steadily increasing in their severity and size over the past 100 years, with 7 of the largest fires occurring since 2003.
Part of the observed recent rise in wildfires is also the result of past fire management gone wrong. Wildfires are part of the natural cycle in the Southwestern United States. From time to time, fires will consume old or dead vegetation, making space for new plants and the ash fertilizing the soil. However, for about a century, California focused on quickly extinguishing fires rather than allowing for controlled burns, causing dead vegetation to accumulate. The surplus of flammable material in the forest’s undergrowth now feeds much larger flames, that driven by wind will quickly spread into their surroundings.