Throughout history, drought is constant threat to societies around the world. What do proxy records tell us about the severity, extent and causes of drought during the last thousand years?

1. GEOG5426 Megadrought I

2. No class October 6!
(I’m going to Boulder)

6. 100 Views of Climate Change h p://changingclimates.colostate.edu/

7. 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).

9. Sco Stine California State University

10. Mono Lake flickr.com: kla4067

11. Water transfers in the American southwest
Courtesy Glen MacDonald

12. LA Aqueduct flickr.com: Aquafornia

13. Second LA Aqueduct at Jawbone Canyon flickr.com: Aquafornia

14. LA Aqueduct Filtration Plant flickr.com: Aquafornia 14

16. Submerged stumps in Mono Lake

17. Radiocarbon ages of “drought terminations Stine, Nature, 1994

18. Radiocarbon ages of “drought terminations Stine, Nature, 1994

19. * One sigma errors
Radiocarbon ages of “drought terminations Stine, Nature, 1994

20. “Medieval Climate Anomaly”

21. Submerged tree stumps in Lake Bosumtwi Ghana

22. Ed Cook Lamont-Doherty Earth Observatory

23. Ed Cook Lamont-Doherty Earth Observatory

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

25. Tree-ring chronologies Cook et al., JQS, 2010

26. Palmer Drought Severity Index
The 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.

27. 25

28. The NADA grid Cook et al., Science, 2004

29. Drought Area Index

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

31. Tree-ring chronologies Cook et al., JQS, 2010

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

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

34. PDSI estimates during the Stine megadroughts Cook et al., JQS, 2010

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

37. “Medieval Warm Period”
What evidence do Cook et al. present to support their
claim that the medieval period was unusually warm?

38. Dave Meko University of Arizona

39. Colorado River Arizona
Photograph: Al_HikesAZ

40. Water transfers in the American southwest
Courtesy Glen MacDonald

41. Colorado River Compact
1922

42. Observed discharge, Colorado River
Compact allocation (16.5 MAF)

43. The history of precipitation and runoff in the
Colorado Basin as indicated by tree-rings
Edmund Shulman
Ph.D. Thesis
Harvard University
1944

44. Relic tree, circa 323 BC Harmon Canyon, Utah

45. Colorado River basin tree rings Meko et al., GRL, 2007

46. “Natural” flow
The best estimate of river discharge in the absence of
human modifications to the hydrological system

47. 1,200 years of Colorado River discharge Meko et al., GRL, 2007

50. Drought proxies in the western US Meko et al., GRL 2007

51. “ The tree-ring record shows that droughts
lasting decades have routinely gripped
western North America.”
Jonathan Overpeck and Bradley Udall

52. “ 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

53. Informal student survey
Please don’t sign the sheets