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Acres Burned in Washington

As this graph clearly shows, the acreage burned by wildfires in the state of Washington has increased significantly in recent years. All told, more land burned during the years 2000-2007 than burned in the decades 1977-1999 combined.

This is consistent with a broader pattern across the American west, where rising temperatures and increased destruction from wildfires are highly correlated. One key link is that higher temperatures in spring can cause earlier snowmelt, which makes for a longer and more severe fire season.

The graph begins in 1977 because that is the year when the Pacific Decadal Oscillation, or PDO—a periodic shift in Pacific sea surface temperatures that happens every 20 or 30 years and influences climate patterns on land—changed from a relatively cool to a relatively warm phase. The graph ends in 2007, the last year that full sets of fire data were available. At that point the PDO was still in a warm phase; this is important because comparing fire data within the same PDO phase gives a cleaner picture of climate influences that go beyond natural variability.

Data were provided by Jeremy S. Littell, Climate Impacts Group, Joint Institute for the Study of the Atmosphere and Ocean and Center for Science in the Earth System (JISAO/CSES), University of Washington, and were published in a 2009 paper (Abstract) in the journal Ecological Applications. Data are compiled from the USDA Forest Service and Department of Interior annual fire statistic reports and the archives at the National Interagency Fire Management Database.1

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