READING FOR THURSDAYDavid Meko and Connie Woodhouse (2010), Application of streamflow reconstruction to water resources management. M.K. Hughes et al. (eds.), Dendroclimatology, Developments in Paleoenvironmental Research.

QUESTIONWhat was Denver Water’s key concern regarding its water supply?

QUESTIONWhat specific test did Denver Water use to assess whether or not tree rings were skillful estimators of river flow?

h!p://www.ldeo.columbia.edu/tree-ring-laboratory/

Ed Cook Lamont-Doherty Earth Observatory

Observed discharge, Colorado River

Compact allocation (16.5 MAF)

Low reservoir

Photograph: Glen MacDonald

[The early 21st century drought] highlights both the extreme vulnerability of the semi-arid western United States to precipitation deficits and the need to be!er understand long-term drought variability and its causes in North America.

“”Cook et al., 2004

To this end, we have used centuries-long, annually resolved tree-ring records to reconstruct annual changes in both drought and wetness over large portions of North America.

“”

Cook et al., 2004

T H E N O R T H A M E R I C A N D R O U G H T A T L A S

Tree-ring chronologies (red dots) 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.

+4 extreme wet

-4 extreme drought

(compared to ‘average’ for that place)

One hundred years of drought history around Minneapolis-St. Paul

Source: North American Drought Atlas

Drought grid (blue dots) Cook et al., JQS, 2010

Network reconstruction

Drought grid (blue dots) Cook et al., JQS, 2010

Source: Woodhouse et al., 2006

Average PDSI, AD 1580 to 1600

HOW DO WE KNOW

THIS WORKS?

empirical comparisons

Dalhart, TX, 1938

Source: David Stahle

Tree ring

Source: David Stahle

June 1833All-time record flooding on the Arkansas, Canadian, and Verdigris Rivers in Oklahoma. 950 displaced Creek and Seminole drown on floodplain farmsteads.

Source: David Stahle

Source: David Stahle

Tree-ring records through time Cook et al., Science, 2004

Quality of PDSI estimates from tree rings Cook et al., JQS, 2010

WHY RECONSTRUCT THE

PDSI?

Source: David Stahle

St. George et al., The Holocene, 2010

Seasonal precipitation ‘bias’ of NADA

APPLICATIONS

Cook et al., 2007, Earth Science Reviews

How has the extent of severe drought changed through time?

Observed (blue) and tree-ring (red) PDSI in ‘The West’

A 1,000 years of drought in the West Cook et al., Science, 2004

How do other aspects of the climate system influence the

frequency or severity of drought?

EL NIÑ0SOUTHERN OSCILLATION

Source: St. George et al., 2010

Can the Drought Atlas help us place historical events within a context of long-term environmental change?

Square Tower HouseMesa Verde, Colorado

Source: David Stahle

Square Tower HouseMesa Verde, Colorado

Great Pueblo DroughtA.E. Douglass (1929)

Source: David Stahle

North American Drought Atlas h!p://www.ncdc.noaa.gov/cgi-bin/paleo/pd08plot.pl

Source: Ingmar Zahorsky

Much of the world’s population lives in monsoon Asia and depends on monsoon rainfall for water and agricultural fertility.

“” Wahl and Morrill, 2010

E R Wahl, C Morrill Science 2010;328:437-438

Average spatial pa!erns of precipitation and wind during summer

MONSOON ASIA DROUGHT ATLAS

h!p://www.ncdc.noaa.gov/paleo/pubs/cook2010/cook2010.html

Photograph: Kevin Anchukaitis

Tree-ring records across Monsoon Asia

E R Cook et al. Science 2010;328:486-489

E R Cook et al. Science 2010;328:486-489

Tree rings show extent of ‘Great Drought’, 1876-1878

E R Cook et al. Science 2010;328:486-489

Was the ‘Great Drought’ caused by ENSO or the North Pacific Ocean?

The MADA is a crucial step forward for paleoclimate studies in a region that is of great social and climatological interest, but where the development of tree-ring archives faces immense challenges and instrumental data coverage is limited.

“”

Wahl and Morrill, 2010

READINGEugene Wahl and Carrie Morrill (2010), Toward understanding and predicting monsoon pa!erns. Science 328, 437-438.

GRADUATE STUDENT READINGBüntgen et al. (2011), 2500 years of European climate variability and human susceptibility. Science 331, 578-582.