I've been asked to give a presentation at a workshop to be held in Alberta in March. The workshop will revolve mainly around the use of tree rings and other natural 'proxy' records to water issues in the Canadian Prairie provinces. I'll be presenting material drawn from the last chapter of my doctoral dissertation, and will talk about the strengths and limitations of tree-ring records as indicators of past drought. The audience will include between 50 and 100 water managers from the region, and for many of them, the workshop will be their first exposure to tree rings and other forms of paleoclimatology. I think it will be in their best interest (and mine) that the scientific presentations focus more on big-picture ideas and less on technical details and methodology. With an eye towards getting my point across more effectively, I've worked up a set of slides in the 'Presentation Zen' style. I've included more photos than I have in previous presentations, and have also tried to swap out complex journal-style diagrams and replace them with simpler graphics. I'm excited (and a little nervous) to see how the presentation is received - I imagine its style will be quite different from the other talks in the workshop. I've posted the slides at Slideshare.net, and would appreciate any comments or suggestions - the workshop is not for another six weeks, so I have plenty of time left to tweak or change my plans.

1. Tree Rings and Drought
Past drought on the Canadian Prairies
S co tt St. Ge orge
Geological Survey of Canada

2. Prairie tree-ring network, ca. 1996

3. 3

5. Fort Dufferin, Manitoba

6. 4,000 year-old
river logs
6

7. Prairie tree-ring network
Northern Saskatchewan
Eastern Rockies
Northwestern
Ontario
Southern Manitoba

8. 4
Characteristics of
Prairie tree rings

9. The tree-ring record of summer
drought in the Canadian Prairies
Scott St. George
David Meko Greg Pederson
Martin-Phillippe Girardin David Sauchyn
Glen MacDonald Jacques Tardif
Erik Nielsen Emma Watson
Submitted to the Journal of Climate, January 2008

10. Tree age

11. Bristlecone pine
4,844 years
Source: OLDLIST
Photo: Tom Harlan

12. Eastern white cedar
1,653 years
Source: OLDLIST
Photo: Peter Kelly

13. Eastern white pine
290 years
Source: M. Girardin

14. Bur oak
279 years

15. Limber pine
846 years
Source: G. Pederson
Photo: Greg Pederson

16. Richard I of England 16
Photo: julie & fanu

17. Length of regional records
S. Alberta 480
N. Saskatchewan 169
S. Manitoba 485
NW Ontario 225
0 125 250 375 500
Years

18. Seasonality

19. “
The trees composing the
forest rejoice and lament with
its successes and failures and
carry year by year something
of its story in their annual
rings.
”Douglass
A.E.

20. Dominant seasonal signals
90
82
80
70
60
50
Sites
40
30 24
20
10 7
3
0 20
Autumn Winter Spring Summer Autumn

21. 21

22. 22

23. Medicine Hat, Alberta
Source: Environment Canada, Adjusted Historical Canadian Climate Data, 1895 – 2006

24. 24

25. Effectiveness

26. Dendrohydrology
works best where it’s
dry ...

27. and not so well
where it’s
wet

28. Ringwidth as a proxy for
‘Lethbridge’ PDSI

29. Ringwidth as a proxy for
‘Dryden’ PDSI

30. Uncertainty

31. 755 m3/s
847 m3/s
809 m3/s
770 m3/s
823 m3/s
787 m3/s
901 m3/s
3

32. “Trees are not thermometers
or raingauges.”
Keith Briffa and colleagues

33. Quantitative drought estimates

34. Quantitative drought estimates

35. Can we
Absolutely!
do better?

36. Photo: Emma Watson

38. Photo: New York Times
38

39. Focus on long-term drought
100% 60% 43%
Explained variance
75%
50% 57%
40%
25%
0%
Single Year 5-Year Average

40. Courtesy Keith Lombardo
Measure other stuff
Wood chemistry Wood density
Stable isotopes Wood anatomy

41. Prairie tree rings
& drought
41

42. Photo: Monceau
web.mac.com/scottstgeorge