HR: 08:30h
AN: U51A-03 INVITED     [Abstracts]
TI: Climate-Change Uncertainties and Water Supplies from Western Mountains--What are Observations and Models Trying to tell us?
AU: * Dettinger, M
EM: mddettin@usgs.gov
AF: U.S. Geological Survey, Scripps Institution of Oceanography, UC San Diego, Dept 0224 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Cayan, D
EM: dcayan@ucsd.edu
AF: U.S. Geological Survey, Scripps Institution of Oceanography, UC San Diego, Dept 0224 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Stewart, I
EM: iris@pangea.stanford.edu
AF: Scripps Institution of Oceanography, UC San Diego, Dept 0224 9500 Gilman Drive, La Jolla, CA 92093 United States
AU: Knowles, N
EM: noah_k@earthlink.net
AF: U.S. Geological Survey, 345 Middlefield Road, MS496, Menlo Park, CA 94025 United States
AB: In recent decades, snowmelt and streamflow timing in the river basins of the mountains of western North America have changed in response to warmer winters and springs. The observed hydrological trends toward smaller snowpacks and earlier runoff are widespread and significant. Although these trends partially reflect natural interdecadal regimes of the Pacific-North American climate system, a large component of the recent changes can be attributed to even broader global-warming trends. The future of these temperature, snowpack, and streamflow trends in the mountainous West are uncertain and some of the key uncertainties at this regional scale are unlikely to be eliminated soon. Nonetheless, long-term resource-management planning will need to consider the likely hydrologic changes soon because important long-term plans are being made in many settings and because the changes are already underway. To date, climate-change uncertainties typically have been addressed by projecting the impacts of one or two climate-change projections, chosen based on availability or to capture the extremes among available projections. However, characterizing the overall statistical distributions of changes in a moderately large projection ensemble provides new insights into the projections: (i) uncertainties associated with future emissions are comparable with the uncertainties due to model differences, so that neither source of uncertainties should be neglected or underrepresented; (ii) projections of 21st Century temperatures are broadly in consensus but spread and change more overall than do future-precipitation scenarios, so that performance of water-resource systems under near-term temperature changes is particularly pressing; (iii) projections of extremely wet futures for the West are statistical outliers among current projections; and (iv) the current projections that are warmest tend, overall, to yield a moderately drier California, while the cooler projections yield a somewhat wetter future. These findings should be considered in plans and assumptions about future observational systems, snowpack and streamflow, and water supplies in western mountains.
DE: 1699 General or miscellaneous
DE: 1863 Snow and ice (1827)
DE: 1884 Water supply
SC: Union [U]
MN: 2004 AGU Fall Meeting