A study, utilizing scenarios for future climate change based on the results of two global climate models, has provided the most detailed projection yet of the potential environmental and societal impacts on California resulting from the climatic change due to increasing greenhouse gas concentrations. California was chosen for this study due to its diverse range of climates, limited water resources, and the existence of a large number of climate-sensitive industries such as agriculture. This study was authored by 19 scientists from various research institutions and universities, including the Scripps Institution of Oceanography, U.S. Geological Survey, and Stanford University.
Even assuming that emission reduction policies are implemented and the use of renewable energy is significantly increased, annual average temperature is projected to increase by 2.3 to 3.3ºC (4.0 to 5.9ºF) by the end of the century. As a result of the temperature increase, heatwaves are likely to become four times more frequent and heat-related excess mortality is projected to increase by two to three times. The Sierra Nevada snowpack, which is a large water source for various municipal and agricultural areas in California, is projected to decrease by 30-70%.
Alternatively, assuming that fossil fuel use continues to increase at the present pace and in the absence of any aggressive emissions reduction policies, by the end of the century, temperatures in California are projected to increase by roughly 3.8 to 5.8ºC (6.8 to 10.4ºF), with greater increases in the summer than in the winter. Heatwaves and extreme heat in Los Angeles are projected to become six to eight times more frequent -- with heat-related excess mortality increasing five to seven times. Moreover, the projected snowpack reduction of in the Sierra Nevada ranges from 73- to 90%. Due to significant decreases in runoff and streamflow, such changes would cause severe disruption of the already tightly allocated water resources, causing devastating impacts throughout California.
In addition to water resources, the projected changes in climate would be very likely to have detrimental effects on California’s agriculture. For example, the higher temperatures under both emission scenarios will shorten the ripening period for grapes, significantly degrading the quality of the resulting wine. Rising temperatures are also projected to lead to reduction in milk production by as much as 7-10%.
Click here to download the study (PDF, 480KB)
Hayhoe, K., et al. 2004. Emissions pathways, climate change, and impacts on California. Proceedings of the National Academy of Sciences of the United States of America. Vol. 101, No. 3, pp. 12422-12427.
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