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Human-induced changes in the hydrological cycle of the western United States. Tim Barnett 1 , David Pierce 1 , Hugo Hildalgo 1 , Tapash Das 1 , Celine Bonfils 2 , Ben Santer 2 , G. Bala 2 , Art Mirin 2 , Andy Wood 4 , Toru Nozawa 3 , Dan Cayan 1 , Mike Dettinger 1
Tim Barnett1, David Pierce1, Hugo Hildalgo1, Tapash Das1, Celine Bonfils2, Ben Santer2, G. Bala2, Art Mirin2, Andy Wood4, Toru Nozawa3, Dan Cayan1, Mike Dettinger1
1Scripps Institution of Oceanography
2Lawrence Livermore National Lab
3National Inst. Environmental Sciences (Japan)
Anthro causes? Natural variability? Solar / Volcanic forcing changes?
Analyze snowpack, river flow and air temperature simultaneously
These time series are the basis for the fingerprint
Obs snow course
Dividing by P removes majority of correlation between SWE and P
Trend in P (blue) vs. SWE (red), 1950-1999
60% of stations show increasing P, but 71% show decreasing SWE
Trend in the leading EOF of 9 SWE/P timeseries (74%)
PDFs are assembed by resampling control climate runs
S/N ratio is essentially the
standard normal deviate of the fingerprint given control run statistics.
All variables have been normalized (fractionalized) by dividing by the CCSM3-FV control run mean over first 300 yrs.
Necessary for the multivariate detection and attribution (D&A), so have same variance in each variable (the “units problem”).
Q: WHY? ANS: It is ‘US’!
Hidalgo, H. G., M. D. Dettinger, and D. R. Cayan, 2007: Downscaling daily precipitation and temperature fields over the U.S. with constructed analogues. J. Clim., in review.
Wood, A. W., L. R. Leung, V. Sridhar, and D. P. Lettenmaier, 2004: Hydrologic implications of dynamical and statistical approaches to downscaling climate model outputs. Climatic Change, 62, 189-216.
Barnett, T. P., D. W. Pierce, H. G. Hidalgo, C. Bonfils, B. D. Santer, T. Das, G. Bala, A. W. Wood, T. Nazawa, A. Mirin, D. R. Cayan, M. D. Dettinger, 2008: Human-induced changes in the hydrology of the western United States. Science, published online 31 Jan 2008, doi:10.1126/science.1152538.
Bonfils, C., B. D. Santer, D. W. Pierce, H. G. Hidalgo, G. Bala, T. Das, T. P. Barnett, C. Doutriaux, A. W. Wood, A. Mirin, T. Nozawa, 2008: Detection and attribution of temperature changes in the mountainous western United States. J. Climate, in review.
Hidalgo, H. G., T. Das, M. D. Dettinger, D. R. Cayan, D. W. Pierce, T. P. Barnett, G. Bala, A. Mirin, A. W. Wood, C. Bonfils, B. D. Santer, and T. Nozawa, 2008: Detection and attribution of climate change in streamflow timing of the western United States. J. Climate,iIn review.
Pierce D.W., T.P. Barnett, H.G. Hidalgo. T. Das, C. Bonfils, B. Sander, G. Bala, M. Dettinger, D. Cayan and A. Mirin. 2008. Attribution of declining western US snowpack to human effects. J Climate, in review.
Where are we going? And why are we in this hand-basket?