Climate change in CA

Climate change in CA - Global climate change will affect...

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CALIFORNIA AGRICULTURE, MAY-JUNE 2002 89 Bryan C. Weare As we enter the 21st century, it is possible to reach beyond the headlines to describe what is now known about climate change. The Intergovernmental Panel on Climate Change evaluated the scientific aspects of global climate change; the current consensus is described in a recent series of reports. Since the 19th century, concentrations of atmospheric carbon dioxide, methane, nitrous oxide and sulfate aerosol dust have increased significantly. While there is scientific agreement that warming is occurring, the controversy now concerns the extent of subsequent impacts in the future. In California, the impacts of global warming are likely to include reduced water availability and quality, poorer air quality, associated economic consequences, biodiversity shifts and health effects. The changes are expected to continue at an increasing pace well into the next century, perhaps outstripping our scientific, economic and social ability to cope with them. Global climate change will affect air, water in California D uring the past century, perhaps the most controversial subject in atmospheric science has been the ques- tion of whether humans are having a significant impact on climate. Anyone who picks up a newspaper is familiar with conjectures that within this cen- tury, average temperatures will be 5 ° F, 10 ° F or 15 ° F above their current val- ues, precipitation patterns will sub- stantially decrease the water available for agriculture, and a rise in the sea level will flood coastal regions. As we enter the 21st century, it is now pos- sible to reach beyond the headlines and the controversies to describe what is known about climate change in the recent past and what is most likely for the future. It is also possible to sum- marize the likely consequences of glo- bal climate change for California and the southwestern United States. The scientific aspects of global cli- mate change have been evaluated re- cently in a set of extensive reports by the Intergovernmental Panel on Cli- mate Change (IPCC), which were re- leased over several months leading up to a synthesis report (Watson et al. 2001). These reports, compiled by a panel of hundreds of atmospheric sci- entists from around the world under the umbrella of the United Nations, describe the current consensus con- cerning the science of global climate change. This article emphasizes those factors that influence and are influ- enced by agriculture and forestry in the western United States. Few scientists dispute that human activity is causing the atmospheric concentrations of greenhouse gases and particles to increase, and that this, in turn, is leading to global climate change. From about 1900 to the present, concentrations of atmospheric carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) have in- creased substantially (fig. 1). The esti- mates of concentrations before the 20th century are derived mainly from analyses of air trapped in the ice of
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This note was uploaded on 10/16/2010 for the course ESPM C12 taught by Professor Garrisonsposito during the Spring '10 term at Berkeley.

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Climate change in CA - Global climate change will affect...

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