Discover how Climate Signals are related
Climate science at a glance
- Climate change makes it more likely that fires turn into catastrophic blazes through warmer temperatures, increasing the amount of fuel (dried vegetation) available, and reducing water availability through earlier snowmelt and higher evaporation.
- The frequency of hot, dry, and windy weather has increased in much of the US.
- Climate change has doubled the area burned in the western US.
- The fire season has increased by more than two months in the western US, largely due to climate change.
- Climate change has doubled the frequency of autumn days with extreme fire weather conditions in California.
Background information about the 2020 western wildfire season
What factors contribute to worsening wildfires in the western US?
Wildfire disasters are due to the combination of climate change, human land-use and forest management, which can make fires more severe, and the exposure to and vulnerability of populations to fires. Fire officials explain wildfire behavior using the fire triangle, pictured right. Wildfires are driven by three elements: topography (mountainous versus flat), vegetation (the fuel source), and weather. As topography and weather generally cannot be controlled, most fire prevention in wildlands focuses on removing dry vegetation and encouraging healthier ecosystems which won’t burn as easily. In some regions, forest mismanagement has increased wildfire risk.
What were recent western wildfire seasons like?
In 2018, the Camp Fire in Northern California was the costliest, deadliest and most destructive on record, costing an estimated $16.5 billion, killing 85 people, and destroying more than 18,000 structures. The state also endured its largest wildfire on record—the Mendocino Complex Fire, which burned more than 450,000 acres.
California's total wildfire cost in 2018 was a staggering $24 billion, primarily from the destruction of homes and infrastructure, along with firefighting costs. Nationally, the 2018 wildfire season overtook 2017 as the most expensive, and the two years together caused an unprecedented $40 billion worth of damage. The 2017 record was triple the previous record for US annual wildfire season cost, which was $6 billion in 1991.
The 2019 wildfire season, though less destructive than previous years, was notable for a series of significant late-season fires that burned in California. These late fires are consistent with research showing an increase in autumn wildfire risk in the state due to climate change.
What can we expect this season?
The Climate Prediction Center, which is part of the National Weather Service, expects a hotter and drier than average summer across much of the West. A hot summer will intensify already widespread drought in the region, further drying out vegetation and making wildfires worse.
Much of the western US is forecast to see above normal activity. The season could be particularly bad in California due to the combined effect of the most recent winter, which was dry, and the abundance of now dry and flammable vegetation from the previous wet winter.
Last year you’ll remember we had a lot of snow in the mountains, a lot of late-season rain, and we had a slow start to our fire season. That’s not going to be the same this year.
Thom Porter, director of California Department of Forestry and Fire Protection.
How does COVID-19 intersect with wildfire preparedness and response?
- Prescribed burns: Early in the season, firefighters thin out forests using prescribed, or controlled burns to reduce wildfire risk later in the year. However, some agencies are limiting prescribed burns during the COVID-19 pandemic to prevent any effects from smoke that might further worsen conditions for at risk groups. While putting off prescribed burns may be an important health precaution, it could mean worse wildfires this season, and for seasons to come.
- Base camps: Emergency managers must adapt procedures to limit the risk of contagion. When fighting major fires, base camps can number in the thousands and response efforts can last for weeks, often bringing in resources from out of state. Fire personnel will have to undergo regular health checkups, and daily briefings will likely be held virtually to prevent large gatherings. The Department of Interior has a useful primer on Wildfires & COVID-19.
- Evacuations and displacement: Similarly, emergency managers are having to rethink how to prevent the spread of COVID-19 in an evacuation scenario, and how to safely manage displaced populations. The Red Cross, which operates emergency shelters at the request of local officials, is planning major changes to its sheltering practices this year with a focus on numerous, smaller shelters so that social distancing can be maintained.
Having 500 people in a gym with coronavirus, that’s not a smart way to keep the public safe.
Tony Briggs, CEO for the Central California Region of the American Red Cross
How does COVID-19 intersect with wildfire health concerns?
Preliminary research suggests that wildfire smoke could put firefighters and other vulnerable populations at greater risk from the worst complications of the new coronavirus. Research suggests a link between breathing fine particulate matter, like that in smoke, with worsened outcomes from COVID-19. Another study showed habitually breathing wood smoke decreases the lungs’ abilities to clear out pathogens. The Centers for Disease Control and Prevention has published guidance with key messages about managing wildfire smoke amid COVID-19.
Climate signal breakdown
Climate signals #1 and #2: Snowpack decline and snowpack melting earlier and/or faster
Rapid, early snowmelt means a longer dry season, drier vegetation and larger fires in mid- and high-elevation forests. Warmer springs and summers, and the resulting shifts in snowmelt timing, have helped to drive marked increases in burned area in Western forests since the mid-1980s.
Observations consistent with climate signals #1 and #2
- The western US experienced sharp snow water drop-off between mid-April and early May due to both above-average temperatures and a lack of precipitation in many areas, including California, the Pacific Northwest, Nevada and southern Colorado.
- Northern California accrued huge rain and snowfall deficits during a record-dry February. Snowpack in the Northern Sierra rebounded during storms in March and April, climbing back to 69 percent of normal by April 9. However, the second half of April was warm and dry, and snowpack plummeted to 19 percent of normal for early May and disappeared by early June, several weeks ahead of schedule.
Climate signal #3: Extreme heat and heat waves
Due to climate change, extreme heat and heatwaves are becoming more frequent, and this spells trouble for wildfire season in the western US. On a hot summer day, a small spark can ignite a raging wildfire, and data shows that many more wildfires burn in hotter years.
Between 1901 and 2016, the average annual temperatures in the Southwest and Northwest increased by 1.6°F (0.9ºC), and nearly 2°F (1.1°C) respectively. Scientists have found a direct link between increasing heat extremes in the West and human-caused climate change. As the West heats up, conditions are primed for wildfires to ignite and spread. During the period 1980 to 2010, there was a fourfold increase in the number of large and long-duration forest fires in the American West, and the size of wildfires increased severalfold.
Observations consistent with climate signal #3
- California has experienced an unusually high number of early-season heatwaves already this season.
Climate signal #4: Drought risk increase
The Western United States in the midst of an extreme megadrought, among the worst in recorded history, and rising temperatures due to human-caused climate change are responsible for about half the pace and severity of the drought.
This year, like the previous five to 10 years, has water managers working their worry beads.
Bill Patzert, climatologist
Observations consistent with climate signal #4
In California, the 2019-2020 water season reflects the underlying megadrought. California had an abnormally dry January, its driest February on record, and the average statewide temperature in winter (Dec-Feb) was 2.7°F above the 1901-2000 average.
In Arizona, little rain had fallen by mid-July, despite June 15 marking the start of the state’s official monsoon season. In June, Arizona experienced three major fires among the top 10 biggest wildfires in state history.