California’s catastrophic wildfires, massive tree mortality and water crisis can be partly blamed on human-induced climate change, according to a new report by Columbia University’s Lamont-Doherty Earth Observatory.
Researchers estimate greenhouse gas emissions have deepened the gripping four-year drought by approximately 15 to 20 percent.
“Meaning that in the absence of global warming, probably the drought would be 15-20 percent less severe,” said Park Williams, a climate scientist at Columbia University and the lead author of the study.
Williams and his team analyzed monthly soil moisture levels, temperatures and wind speeds from nearly 24,000 locations across California, dating back 114 years. They found temperatures across California have increased nearly 2 degrees in just the last 45 years.
“That has translated into the atmosphere demanding about three-and-a-half extra inches of precipitation each year,” Williams said.
A warmer atmosphere can hold more water vapor and extracts more moisture from the soil. And while a large portion of California’s drought can be tied to natural weather variabilities, such as a lack of rainfall or ridge of high pressure, warming temperatures have exacerbated the bone-dry conditions.
Williams said California is expected to become temporarily wet this winter from El Niño — another natural variability — but warming temperatures will likely worsen future droughts.
He likens climate change to a “bully who is getting meaner and meaner over time.”
“The bully is always setting records every year in terms of how greedy he is,” Williams said. “And we are now at a point where the bully’s asking for so much that when natural climate variability is already dictating that we would be in a drought, it is difficult to both give the bully the amount of moisture that he needs and also still to satisfy our own demands for moisture.”
