Increase in large California fires being driven by climate change
New research from the Earth Institute at Columbia University has found a strong connection between the increasing trend of large California wildfires and arid ground conditions brought on by climate warming.
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2019/590x442_07171458_dfg.jpg"/>
Average summer temperatures for the state of California have increased 3.25 degrees Fahrenheit since 1896, with 75 percent of this increase occurring since the early 1970s, according to the Columbia University <a href="https://blogs.ei.columbia.edu/2019/07/15/study-bolsters-case-that-warming-climate-is-driving-many-california-wildfires/" target=n>State of the Climate report.</a>
The total area burned annually in the state of California from 1972-2018 has increased fivefold, due in part to a more than eightfold increase in summer fires, according to the report, which was led by Park Williams, a bioclimatologist at Columbia University’s Lamont-Doherty Earth Observatory.
<u>Image below shows area burned by California wildfires in thousands of square kilometers, 1972-2018. Credit Williams et al., 2019</u>
<img src="https://vortex.accuweather.com/adc2004/pub/includes/columns/climatewx/2019/590x391_07171442_williams-calif-wildfire-2019-637x423.jpg"/>
When the air heats up, even slightly, it causes more moisture to evaporate from the soil and vegetation. The result of this is a situation where fires can start much more easily and spread faster and farther, according to the study.
<strong>Key excerpt from the Columbia report.....</strong>
<em>The premise that warmer air draws moisture from the ground level — a phenomenon known as vapor pressure deficit — is already well established. However, many confounding factors can shift fire risk up or down, and so it is not always possible to measure the effects of vapor pressure deficit. In California, human infrastructure is sprawling into forests, introducing more chances for people to both cause fires and suffer from them. And a century of efforts to suppress virtually all fires has led to a buildup of flammable materials in many forests. On the other hand, fragmentation of forest landscapes by human intrusion may in some cases limit the spread of fires. Rainfall and snow can vary year to year, sometimes adding to fire risk, sometimes subtracting. And areas dominated by shrubs or grasses instead of trees may not react the same way.</em>
Looking through more than a hundred years of data, the team determined that growing temperature-induced vapor pressure deficit accounted for nearly all the growth in forest fires from 1972-2018.
The study concludes that California wildfires could grow exponentially in the next 40 years as the climate continues to warm due to the further increase in greenhouse gas emissions.
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This is a link to the <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019EF001210" target=n>actual study.</a>
