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.

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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