Class 5, Megadrought i
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Transcript of Class 5, Megadrought i
GEOG5426 Megadrought I
No class October 6!
(I’m going to Boulder)
100 Views of Climate Change h!p://changingclimates.colostate.edu/
Workload A paper, not to exceed 10 pages of text plus figures and references, which reviews the climate history of a single region over a specific time period during the Holocene (e.g., the mid-Holocene, the last 2ka or the last 500 yr).
Sco! Stine California State University
Mono Lake flickr.com: kla4067
Water transfers in the American southwest
Courtesy Glen MacDonald
LA Aqueduct flickr.com: Aquafornia
Second LA Aqueduct at Jawbone Canyon flickr.com: Aquafornia
14LA Aqueduct Filtration Plant flickr.com: Aquafornia
Submerged stumps in Mono Lake
Radiocarbon ages of “drought terminations Stine, Nature, 1994
Radiocarbon ages of “drought terminations Stine, Nature, 1994
Radiocarbon ages of “drought terminations Stine, Nature, 1994
* One sigma errors
“Medieval Climate Anomaly”
Submerged tree stumps in Lake Bosumtwi Ghana
Ed Cook Lamont-Doherty Earth Observatory
Ed Cook Lamont-Doherty Earth Observatory
North American Drought Atlas h!p://www.ncdc.noaa.gov/cgi-bin/paleo/pd08plot.pl
Tree-ring chronologies Cook et al., JQS, 2010
Palmer Drought Severity IndexThe PDSI incorporates historical records of precipitation and temperature into a water-balance model to estimate
the amount of water available in the soil relative to average conditions and is typically produced once a month.
25
The NADA grid Cook et al., Science, 2004
Drought Area Index
Observed (blue) and tree-ring (red) PDSI in ‘The West’
Tree-ring chronologies Cook et al., JQS, 2010
Tree-ring records through time Cook et al., Science, 2004
Quality of PDSI estimates from tree rings Cook et al., JQS, 2010
PDSI estimates during the Stine megadroughts Cook et al., JQS, 2010
A 1,000 years of drought in the West Cook et al., Science, 2004
“Medieval Warm Period”What evidence do Cook et al. present to support their
claim that the medieval period was unusually warm?
Dave Meko University of Arizona
Photograph: Al_HikesAZ
Colorado River Arizona
Water transfers in the American southwest
Courtesy Glen MacDonald
Colorado River Compact1922
Observed discharge, Colorado River
Compact allocation (16.5 MAF)
The history of precipitation and runoff in the Colorado Basin as indicated by tree-rings
Edmund Shulman Ph.D. Thesis Harvard University 1944
Relic tree, circa 323 BC Harmon Canyon, Utah
Colorado River basin tree rings Meko et al., GRL, 2007
“Natural” flowThe best estimate of river discharge in the absence of
human modifications to the hydrological system
1,200 years of Colorado River discharge Meko et al., GRL, 2007
Drought proxies in the western US Meko et al., GRL 2007
The tree-ring record shows that droughts lasting decades have routinely gripped western North America.”
“Jonathan Overpeck and Bradley Udall
As western North America currently endures its worst drought since 1900, it is important to realize that this drought might be nothing compared to what is possible in the future if megadrought and even ho!er temperatures coincide.”
“Jonathan Overpeck and Bradley Udall
Informal student surveyPlease don’t sign the sheets