California Gov. Jerry Brown (D) blamed global warming for California wildfires this spring, but objective scientific data show a decline in wildfires as the planet modestly warms.
Unusually Quiet Wildfire Seasons
The year 2013 was one of the quietest years for wildfires in U.S. history, according to data from the federal government’s National Interagency Fire Center. The 47,000 wildfires last year may seem like a very large number, but that number was less than half the average number that occurred each year in the 1960s and 1970s. Importantly, the Earth was in a cooling phase during the 1960s and 1970s when so many more wildfires occurred.
The unusually quiet 2013 fire season continued a long-term decline. From 1962 through 1982, at least 100,000 wildfires occurred in the United States every year. Since 1982, however, not a single year has registered 100,000 wildfires. During the past decade, an average of 73,000 wildfires occurred each year. During the 1970s, the annual average was 155,000 wildfires.
The 2014 wildfire season has been relatively quiet so far, with a total number of wildfires well below the 1962-2013 average and even below the average for the past decade. Even so, alarmists have used the below-average 22,000 wildfires so far this year as opportunities to claim a connection between warming and wildfires.
Shifting Wildfire Strategies
Global warming activists often note a larger number of acres have been subject to wildfires in recent years, but that primarily reflects a recent change in the federal government’s wildfire management policy. Throughout most of the twentieth century, U.S. forest managers attempted to put out all wildfires, regardless of cause, as quickly as possible. Near the end of the century, however, forest managers realized this led to unnatural forest density which brought many unintended consequences. In recent years, forest managers have let natural wildfires burn themselves out naturally, focusing their efforts on protecting human lives and property rather than absolute fire suppression.
Despite this more permissive approach to fire suppression, the number of wildfires continues to decline as the Earth modestly warms.
Drought Conditions in Decline
A scientific study in the peer-reviewed Journal of Hydrology affirms the drought conditions that facilitate wildfires have declined throughout the past century. The study reports, “Evidence indicates that summer soil moisture content has increased during the last several decades at almost all sites having long-term records in the Global Soil Moisture Data Bank.”
Similarly, a scientific study in the peer-reviewed Geophysical Research Letters reports, “An increasing trend is apparent in both model soil moisture and runoff over much of the U.S.… This wetting trend is consistent with the general increase in precipitation in the latter half of the 20th century. Droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the country over the last century.”
James M. Taylor ([email protected]) is managing editor of Environment & Climate News.
National Interagency Fire Center, Total Wildland Fires and Acres, http://www.nifc.gov/fireInfo/fireInfo_stats_totalFires.html
Huntington, G., “Evidence for intensification of the global water cycle: Review and synthesis,” Journal of Hydrology, 2006, http://www.ic.ucsc.edu/~mdmccar/ocea213/readings/discuss_1_Oki_Huntington/Huntington_2006_JHydrol_Evidence_intensification_Hydrologic_cycle.pdf
Andreadis, K. and Lettenmaier, D., “Trends in 20th century drought over the continental United States,” Geophysical Research Letters, 2006, http://onlinelibrary.wiley.com/doi/10.1029/2006GL025711/abstract