Climate change could have drastic impact on California

Global climate change could significantly alter life in California by the end of the century, according to a study co-authored by Stanford University researchers published in the Aug. 16 online edition of the Proceedings of the National Academy of Sciences (PNAS).

"More frequent heat waves, dramatically reduced Sierra snowpack and decreased quality of wine grapes are in California's future, unless we take action now to minimize climate change," said Christopher Field, a professor, by courtesy, of biological sciences at Stanford and director of the Carnegie Institution's Department of Global Ecology.

Field is one of 20 co-authors of the PNASstudy representing 13 institutions and organizations. The other Stanford co-authors are Stephen H. Schneider, professor of biological sciences and senior fellow at the Stanford Institute for International Studies, and graduate students Kimberly N. Cahill, Elsa E. Cleland and Claire K. Lunch.

Two scenarios

In their study, the researchers used sophisticated computer models to predict how California's climate could change by 2100. The computer projections were based on two possible scenarios:

  • State policymakers continue to rely on oil, coal and other traditional fossil fuels that release high levels of carbon dioxide and other greenhouse gases into the atmosphere.
  • The state makes an extensive investment in solar, wind and other renewable energy sources that do not emit heat-trapping gases.

Computer analysis revealed that California's climate would be significantly altered under either scenario, although the changes would be less severe if there was a sharp reduction in fossil fuel use in the next 50 years.

Take heat waves. A "heat wave" is defined as three or more consecutive days where the temperature is above 89.6 F. Between 1961 and 1990, Los Angeles averaged 12 heat wave days annually. But the research team found that if nothing is done to reduce greenhouse gas emissions, the city could experience 95 heat wave days by the end of the century. However, if greenhouse gas emissions are significantly reduced statewide, then Angelenos will likely face 44 heat wave days by 2100. Likewise, if fossil fuel use in Los Angeles continues at its present level, the number of heat-related deaths could increase sevenfold, compared to a threefold increase if greenhouse gases are lowered.

Snow, milk and wine

The study also predicted that snowpack in the Sierra Nevada ­ a vital source of water ­ would decrease by 70 percent if fossil fuels remain the primary energy source and by 30 percent under the renewable energy scenario. In either case, the decline "will impact 85 percent of California's population who are agricultural and urban users in the Central Valley, San Francisco Bay Area and the South Coast," the authors concluded.

Computer analysis also forecast that milk production would be reduced 7 to 22 percent in the state's top 10 dairy counties, and that wine grape production would be impaired statewide except in cool coastal vineyards. Meanwhile, between 50 and 75 percent of the state's alpine forests will disappear in 100 years, the researchers predicted.

Overall, the study showed that the amount of climate change and the severity of its impacts can be cut by 50 percent or more if greenhouse gas emissions are reduced in coming decades.

"Leadership in developing innovative technologies, policies and strategies can pave the way to a much more positive future," Field said. "We truly have a choice."

The study was also co-written by researchers from ATMOS Research and Consulting in South Bend, Ind.; Scripps Institution of Oceanography; Union of Concerned Scientists; Santa Clara University; Lawrence Berkeley National Laboratory; National Center for Atmospheric Research; U.S. Forest Service; University of California-Berkeley; University of California-Santa Barbara; University of Delaware; and Kent State University.

The study was supported by the David and Lucile Packard Foundation; the William and Flora Hewlett Foundation; the Energy Foundation; the California Energy Commission; the National Oceanic and Atmospheric Administration Office of Global Programs; and the U.S. Department of Energy.