National Research Program

Climate Change in the Western United States:

Evidence of earlier spring


Map of spring temperature trends 1950-1997 and chart showing relationship of temperature and lilac blooms in the Western United States [Graph relates spring temperature trends from 1950-1997 to lilac blooms in the Western United States]

The onset of spring in the Western U.S. has been earlier from the late 1970's to the present than it was from the mid-1950's to the late 1970's. These results, published in the March 2001 Bulletin of the American Meteorological Society, are based on evidence from the timing of snowmelt-runofff pulses and changes in the blooming of lilac and honeysuckle bushes. The pattern of earlier spring onsets over much of the west is consistent with warmer than normal temperatures in western North America. It is unclear whether this is predominantly an expression of natural variablity or a symptom of global warming.

The American Meteorological Society has provided open access to the complete article, Cayan, D.R., Kammerdiener, S.A., Dettinger, M.D., Caprio, J.M., and Peterson, D.H., 2001, Changes in the onset of spring in the western United States: Bulletin of the American Meteorological Society, v. 82, p. 399-415 (in pdf format, 1.06 MB, published by the American Meteorological Society with open access). For related information, see the project Geochemistry of Riverine and Estuarine Waters or contact:

Daniel R. Cayan, U.S. Geological Survey and Scripps Institution of Oceanography, La Jolla, California

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