Study shows climate change made Calif. drought less likely to occur

jerry brownA new peer-reviewed study refutes Gov. Jerry Brown’s assertion that global warming is behind California’s drought, indicating that climate change neither makes droughts more likely to occur nor exacerbates them. The study, published this week in the Journal of Climate, shows that the “net effect of climate change” has made California’s agriculture drought “less likely” to occur and that the “current severe impacts of drought on California’s agriculture” has not been exacerbated by long-term climate changes. This is another stinging indictment that Gov. Brown’s belief that global warming is causing California’s drought is bordering on wish fulfillment.

As first reported here, two earlier studies also show that natural variability, and not global warming, are behind California’s four-year-long drought. An untimely combination of natural events is occurring, but unfortunately for Brown, they have nothing to do with global warming.

This hasn’t stopped Gov. Brown from blaming the drought, and wildfires, on climate change and making it one of his key talking points during press events and educational summits. More puzzling, Brown’s drought statements have gotten more forceful and extreme, even as the science is telling a far different story. Even the NY Times jumped on the bandwagon, quoting one climate scientist who said global warming has made the drought even worse, but admitting that without climate change, it would be a “fairly bad drought no matter what.”

This most recent study looked at how global radiative forcing (the difference between how much sunlight is absorbed by the Earth and radiated back to space.) influences long-term climate change in California, specifically on its drought. Using observations and computer models, the simulations show that increased “radiative forcing since the late 19th Century induces both increased annual precipitation and increased surface temperature over California.” This, they write, is consistent with observed long-term changes (what is actually measured) and previous computer model studies (what is expected to happen).

What the authors found was “no material difference in the frequency of droughts” defined using various, multiple indicators of “precipitation and near-surface (10 cm) soil moisture.” That’s because shallow soil moisture is more responsive to “increased evaporation driven by warming,” which makes up for the “increase in the precipitation.” Conversely, when using deep soil (~1 meter), “droughts become less frequent” because deep soil moisture is more responsive to “increased precipitation.”

Put simply, the study shows how different land surfaces and depths respond to climate changes, which is most pertinent for “near-surface moisture exchange and for root zone moisture availability.” Moisture availability for roots is the most important as the deep layer determines “moisture availability for plants, trees, and many crops.” In the end, it shows that “climate change has made agricultural drought less likely, and that the current severe impacts of drought on California’s agriculture has not been substantially caused by long-term climate changes.”

This should come as good news to Gov. Brown, who fundamentally believes that climate change is causing the severe drought in his state, even though historical records indicate that long-running droughts have occurred in California for millennia. The last multi-year drought happened in 1976, except climatologists blamed that drought, and the subsequent wildfires, on global cooling, not global warming.

The current drought, though, has been made worse by one thing that nature has little control over: man-made interference in the state’s poorly regulated water system that favors agriculture over availability. Another factor is the much-hyped delta smelt, a tiny fish that environmentalists claimed was endangered and successfully had it listed on the Endangered Species Act in 1993. Since that time, many scientists have concluded that listing the delta smelt was premature and not based on factual evidence.

According to’s Lorraine Yapps Cohen, “Legislation that diverted water into San Francisco Bay was intended to protect the delta smelt mini fish from water pumps.” Because environmentalists were able to get the smelt listed as an endangered species, millions of gallons of agricultural water are dumped into the ocean, in a misguided attempt to save a fish at the expense of people’s livelihoods.

This new study was led by Linyin Cheng of the University of Colorado/Boulder and published in the Journal of Climate, a publication of the American Meteorological Society. Other authors listed are from the Cooperative Institute for Research in Environmental Sciences/Boulder, National Oceanic and Atmospheric Administration (NOAA)/Boulder, and the University of California/Irvine.