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Politics : Politics of Energy -- Ignore unavailable to you. Want to Upgrade?

To: Jorj X Mckie who wrote (47126)	1/31/2014 11:40:13 AM
From: Wharf Rat	Read Replies (1) \| Respond to of 86363

I was there for all of them, including '55 and '64. California May Have Hit Its Driest Point In 500 Years, And The Effects Are Frightening California May Have Hit Its Driest Point In 500 Years, And The Effects Are Frightening For California, 2013 was the driest year since the state started measuring rainfall in 1849. Paleoclimatologist B. Lynn Ingram says that, according to the width of old tree rings, California hasn’t been this dry for about 500 years. huffingtonpost.com

To: Jorj X Mckie who wrote (47126)	1/31/2014 3:31:37 PM
From: Alastair McIntosh	Read Replies (1) \| Respond to of 86363

Mega-droughts throughout the American southwest are normal. The past century has been unusually wet compared to the past millenium. North American droughts of the last millennium Publication Type: Journal Article Authors: Herweijer, C.; Seager, R.; Cook, E. R.; Emile-Geay, J. Source: Journal of Climate, Volume 20, p.1353-1376 (2007) URL:http://www.7minds.org/climate/texts/Herweijer_et_al_JClim07.pdf Abstract: Drought is the most economically expensive recurring natural disaster to strike North America in modern times. Recently available gridded drought reconstructions have been developed for most of North America from a network of drought sensitive tree-ring chronologies, many of which span the last 1000 years. These reconstructions enable us to put the famous droughts of the instrumental record(i.e. the 1930s Dust Bowl and the 1950s Southwest droughts) into the context of 1000 years of natural drought variability on the continent. We can now, with this remarkable new record, examine the severity, persistence, spatial signatures and frequencies of drought variability over the past millennium, and how these have changed with time.The gridded drought reconstructions reveal the existence of successive ’mega-droughts’, unprecedented in persistence (20-40 years), yet similar in year-to-year severity and spatial distribution to the major droughts experienced in today’s North America. These ’megadroughts’ occurred during a 400-year long period in the early-mid second millennium A.D., with a climate varying as today’s, but around a drier mean. The implication is that the mechanism forcing persistent drought in the West and Plains in the instrumental era is analagous to that underlying the mega-droughts of the Medieval period. The leading spatial mode of drought variability in the reconstructions resembles the North-American ENSO pattern: widespread drought across the United States, centered on the Southwest, with a hint of the opposite phase in the Pacific Northwest. Recently, climate models forced by the observed history of tropical Pacific SSTs have been able to successfully simulate all of the major North American droughts of the last 150 years. In each case, cool ’La Niña-like’ conditions in the tropical Pacific are consistent with North American drought.With ENSO showing a pronounced signal in the gridded drought reconstructions of the last millennium, both in terms of its link to the leading spatial mode, and the leading timescales of drought variability (revealed by multi-taper spectral analysis and wavelet analysis), we postulate that, as for the modern day, the Medieval mega-droughts were forced by protracted La Niña-like tropical Pacific SSTs. Further evidence for this comes from the global hydroclimatic ’footprint’ of the Medieval era revealed by existing paleoclimatic archives from the tropical Pacific and ENSO-sensitive tropical and extra-tropical land regions. In general, this global pattern matches that observed for modernday persistent North American drought, whereby a La Niña-like tropical Pacific is accompanied by hemispheric, and in the midlatitudes, zonal, symmetry of hydroclimatic anomalies. southwestlearning.org Many similar papers come up on Google scholar.