9/20/2023 0 Comments California fires![]() “Fire is both fuel- and flammability-limited,” she said. Credit: Brody Hessin, CC BY 4.0, via Wikimedia Commons The Apple Fire burns into the night north of Beaumont, California, on Friday, July 31, 2020. But, as Stavros explains, there are limits. Drier air stresses vegetation, making forests more susceptible to severe wildfires, while droughts are creating more dead fuel. Western wildfires is a greater availability of fuel. More Fuel to BurnĪnother factor driving changes in U.S. land burned by “high-severity” wildfires (fires that destroy more than 95 percent of trees) has increased 800 percent since 1985. Forest Service finds the amount of Western U.S. Another recent study led by Sean Parks of the U.S. ![]() These warmer and drier conditions are also making U.S. Fire seasons are also starting earlier and ending later each year, while snow packs are shrinking, leading to earlier spring snowmelt and longer, more intense dry seasons. According to the National Oceanic and Atmospheric Administration (NOAA), temperatures in California have increased approximately 2 degrees Fahrenheit (1.1 degrees Celsius) since the beginning of the 20 th century. West has warmed, and the frequency and severity of heat waves and droughts has increased. Less warming is expected under a lower emissions future (the coldest years being about 2 degrees Fahrenheit warmer than the historical average green shading) and more warming under a higher emissions future (the hottest years being about 9 degrees Fahrenheit warmer than the hottest year in the historical record red shading). Historically unprecedented warming is projected during the 21st century. Observed temperatures are generally within the envelope of model simulations of the historical period (gray shading). Shading indicates the range of annual temperatures from the set of models. Temperatures in California (orange line) have risen about 2 degrees Fahrenheit since the beginning of the 20th century. Projected changes for 2006–2100 are from global climate models for two possible futures: one in which greenhouse gas emissions continue to increase (higher emissions) and another in which greenhouse gas emissions increase at a slower rate (lower emissions). Observed and projected changes (compared to the 1901–1960 average) in near-surface air temperature for California. ![]() “As climate warms, we’re seeing a long-term drying and warming of both air and vegetation.” “Climate affects how long, how hot and how dry fire seasons are,” she said. Stavros attributes these trends to three primary factors: a changing climate, greater availability of fuel, and the expansion of urban areas, which brings with it more ignitions. Geophysical Research Letters, 41, 2928–2933. Large wildfire trends in the western United States, 1984–2011. Monitoring Trends in Burn Severity-mapped fires are shown in red. The Wyoming Basin and Colorado Plateau ecoregions had too few large fires for trend analysis at the ecoregion level, and are shown in gray. The center map illustrates ecoregions based on Levels II and III of the Omernik ecoregion system. Trends in the annual number of large fires in the western United States for a variety of ecoregions from 1984-2011. ![]()
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