Managing Water Resources in the West Under Conditions of Climate Uncertainty A Proceedings (1991) / Chapter Skim
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4. Primer on Climate Change
4. Primer on Climate Change
Pages 31-46
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From page 31... ...
More certain answers require further improvements in the models. THE BASIS FOR CONCERN ABOUT CLIMATE CHANGE This paper discusses what the scientific community knows and does not know about how the climate and western water resources will change in the future because of increasing greenhouse gas production from human activities.
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From page 32... ...
Most of our present scientific perspective on climate change has been around for more than a decade, and the first scientific discussions of the possible effect on climate of increasing carbon dioxide concentrations date back more than a century. Half a dozen or more assessments of the current scientific consensus have been conducted since 1979, authored by prestigious National Research Council committees and international workshops.
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Various greenhouse gases radiate to space mostly over about the
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Copyright @ 1990 by Cambridge University Press.
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We see the exiting thermal radiation reduced from its surface flux according to characteristic wavelength signatures of the absorbing greenhouse gases and calculable according to greenhouse theory. Another way to appreciate the possible impacts of extreme greenhouse effects is to look at the very hot surface of Venus and the very cold temperature of Mars, also calculable from greenhouse theory.
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From page 36... ...
SOURCE: IPCC, 1990. provided by the oceans, land vegetation, and soils (these compartments each hold more carbon than the total in the atmosphere)
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HOW MUCH WILL OUR HOUSE WARM UP? Given the well-established increasing concentrations of greenaases and reasonably accurate estimates of the resulting house Logo apple 1 Ives, ~___^ ~ increased heating, what does this tell us about future climate change?
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This depends on how easy it is for this extra heat to leak back out again and on what other climate factors the warmer temperatures will change, either to remove some of the excess heat being supplied or to add yet more. How much will the thermal inertia of the system, especially the oceans, delay the warming?
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We develop our sense of the possible and probable by running the most detailed three-dimensional models of our climate system now available and by exploring how the models' outputs depend on poorly described parts of the system. We are currently especially stuck on what clouds might do to change the reflection of solar energy or to change greenhouse warming as climate changes.
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, the dynamics of the oceans and sea ice (especially how the atmosphere couples to these systems) , variations in atmospheric chemical composition, and the climate aspects of land vegetation and soils, including surface hydrology.
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Qualitatively, the projections of global average increasing temperature and precipitation are well founded in basic physical principles and are given by all GCMs. However, a wide range of possibilities for regional anomalies has been suggested by simulations for the changes over regions as small as the western United States (Kellogg and Zhao, 1988~.
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From page 42... ...
The examination of surface hydrology modeled explicitly by GCMs to explore the impacts of climate change on water resources has not yet been carried very far. Emphasis has been primarily on the changes in soil moisture (Manatee and Wetherald, 1987; Meehl and Washington, 1988)
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for the Sacramento Basin under various precipitation changes and warming by 2 and 4°C. SOURCE: Reprinted from Gleick (1987~.
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44 Managing Water Resources 1~1~ / GIST , _,_' FIGURE 4.8 Changes in summer soil moisture in cm for various GCMs. SOURCE: Reprinted, by permission, from Gleick Kellogg and Zhao (1988~.
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Chichester, England: John Wiley & Sons. Intergovernmental Panel for Climate Change (IPCC)
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1979. Geohydrological Implications of Climate Change on Water Resources Development.
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