DROUGHT IN AMERICA DURING THE PAST MILLENNIUM Mark Cane Lamont-Doherty Earth Observatory of Columbia University With Ed Cook, Richard Seager, Amy Clement and Michael Mann Photo: Rose Werner
The New York Times MAY 2, 2004 Drought Settles In, Lake Shrinks and West's Worries Grow PAGE, Ariz. - At five years and counting, the drought that has parched much of the West is getting much harder to shrug off as a blip. Some of the biggest water worries are focused here on Lake Powell... on Niebrugge
The Cathedral in the Desert - before the dam
The Cathedral in the Desert Update: In March 2005 the lake level dropped below the floor level. Another great Lake Powell adventure!
New 1200 year long drought reconstructions from tree-ring records have been produced for most of North America. What can these new drought reconstructions tell us about the relative severity of the current drought?
100 LONG-TERM CHANGES IN DROUGHT AREA IN THE 'WEST' % DROUGHT AREA 80 60 40 20 0 936 1034 DRIER WETTER 1150 1253 1321 THE CENTRAL DATES OF THE SIGNIFICANT (p<0.05) EPOCHS ARE INDICATED WITH ARROWS 1613 WET 1829 1915 Cook et al Science, 2004 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 YEAR The current drought pales next to the epic AD 900-1300 drought period. Why did such an unusually long drought occur? How likely is such a long drought now?
Do the climate models simulate drought? What do they need to know? Is drought predictable? Will greenhouse gases impact drought? Photo: Rose Werner
The 30 s Dust Bowl Multi-year droughts have the greatest social impacts
Precipitation Anomaly 1932-1939 OBSERVED GOGA MODEL Contour interval = 2 mm/month GOGA MODEL = Global Sea Surface Temperature Specified Seager et al 2005
Sea Surface Temperature Anomaly 1932-1939 OBSERVED Contour interval = 0.2 C Kaplan et al 1998
Precipitation Anomaly 1932-1939 POGA-ML MODEL GOGA MODEL POGA-ML MODEL = Only Tropical Pacific Sea Surface Temperature Specified GOGA MODEL = Global Sea Surface Temperature Specified Seager et al 2005
Precipitation Anomaly 1998-2004 OBSERVED GOGA MODEL POGA-ML MODEL OBSERVED SEA SURFACE TEMPERATURE
Precipitation Anomaly 1976-1998 OBSERVED GOGA MODEL POGA-ML MODEL OBSERVED SEA SURFACE TEMPERATURE
Why are there decadal to centennial changes in the tropical Pacific? Photo: Rose Werner
100 LONG-TERM CHANGES IN DROUGHT AREA IN THE 'WEST' % DROUGHT AREA 80 60 40 20 0 936 1034 DRIER WETTER 1150 1253 1321 THE CENTRAL DATES OF THE SIGNIFICANT (p<0.05) EPOCHS ARE INDICATED WITH ARROWS 1613 1829 1915 Cook et al Science, 2004 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 YEAR Returning to the AD 900-1300 epic drought
The Zebiak-Cane El Niño model forced by solar and volcanic irradiance AD 1000-2000 Eastern Equatorial Pacific SST Coral proxy data: Cobb et al 2003 Ensemble mean of model runs From Mann et al 2004 Before 1300 the model - and nature - are more La Niña-like. Irradiance was stronger then. Irradiance EEP SST Drought
Ocean thermostat mechanism (Clement et al. 1996) Normal conditions
Larger temperature response in the West Uniform heating Coupled interactions amplify the East/west temperature difference Cooling by upwelling opposes forcing in the East, reducing temperature response
What happens next, in the greenhouse world? What is happening now? Photo: Rose Werner
20 th Century Temperature Trends -1.0-0.8-0.6-0.4-0.2 0 0.2 0.4 0.6 0.8 1.0 ( C / 100 years) Updated from Cane et al Science 1997
Western droughts can be forced by very small SST anomalies in the tropical Pacific Model response to increased irradiance has the droughtinducing pattern The response is governed by the thermostat mechanism : Increased irradiance colder eastern equatorial Pacific and a stronger zonal temperature gradient at the equator. Photo: Rose Werner
Model results are supported by paleoproxy data Solar-driven changes in the tropical Pacific may have global impacts - including the North Atlantic In the greenhouse future Caveats ZC model is idealized Links in the chain of global connections need further study What is the amplitude of the solar forcing? Photo: Rose Werner
National Oceanic and Atmospheric Administration National Science Foundation
Precipitation (25N-40N, 95W-120W): 1854-2004 Observed POGA-ML ± 2 standard deviations Observed GOGA ± 2 standard deviations Seager et al 2005
Filling Since 1963 The Colorado River Basin is now in its 5th year of drought. Inflow volumes have been below average for 4 consecutive years, with 2004 now certain to follow suit. Low inflows the past 5 years have reduced water storage in Lake Powell. The current elevation (as of September 22, 2004) of Lake Powell Lake Powell has not been this low since 1970 is 3,571 As feet of September (129 feet 22, from 2004: 38% full of pool). capacity Current storage is 9.2 million acre-feet (38% of live capacity). minimum level for power generation = 3490 ft http://www.usbr.gov/uc/water/crsp/crsp_cs_gcd.html
100 LONG-TERM CHANGES IN DROUGHT AREA IN THE 'WEST' % DROUGHT AREA 80 60 40 20 936 1034 DRIER 1150 1253 THE CENTRAL DATES OF THE SIGNIFICANT (p<0.05) EPOCHS ARE INDICATED WITH ARROWS 0 1829 1321 1613 WETTER 1915 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 YEAR 100 DROUGHT TREND IN THE 'WEST': 1900-2003 % DROUGHT AREA 80 60 40 20 CURRENT DROUGHT 0 1900 1920 1940 1960 1980 2000 YEAR Cook et al Science, 2004