How has our climate changed in the past? What caused those changes, and can understanding the Earth’s climate history help us better predict the future? Does the past really matter? In this seminar course, we will examine these questions through the lens of paleoclimatology, which uses physical and cultural evidence to make inferences about climates of the past. We will review the processes that govern our modern climate and explore what paleoclimate records tell us about how these systems respond to (and express) climate change.

1. GEOG5426 Climate variations

2. Observations

3. “ The hills look like sawdust, really,
that colour. I've never seen it where
the grass didn't turn green in the
spring before.”
Jerry Murphy
Elnora, Alberta
source: Globe and Mail, 1 July 2009

5. Examples of key instrumental climate records
(from Bradley, 2008)
Central England temperature 1659
Mean global temperatures 1850
England and Wales precipitation 1766
Southern Oscillation Index 1866
Pacific Decadal Oscillation 1900
Indian Monsoon 1844

7. Climate history of North America
Younger Demise of Laurentide
Dryas Ice Sheet
20 16 12 8 4 0
THOUSANDS OF
YEARS AGO
Final Drainage
of Lake Agassiz
LAST GLACIAL MODERN
MAXIMUM OBSERVATIONS

8. CLIMATE PROXIES
ice cores
tree rings
lake sediments
speleothems
corals

9. GEOG5426 Climate variations
How has our climate changed in the past?
What caused those changes, and can understanding the Earth’s climate history
help us be er predict the future?
Does the past really ma er?

11. Photograph: Rosa Say

12. Photograph: Heidi Barnett
TOOLS Paleolimnology and paleoecology

13. TOOLS Dendrochronology

14. TOOLS Ice cores

15. “Paleoclimatology
reveals what has
actually happened.”
Jonathan Overpeck
University of Arizona

16. Did climate cause the failure of the Jamestown se lement?

17. Did drought and disease affect the Spanish conquest of the Aztec?

18. “There is nothing magical about
the last one hundred years.”
Balaji Rajagopalan
University of Colorado

19. Is the Colorado River over-allocated?
Photograph: Al_HikesAZ

21. MEGADROUGHT
intensity at least equivalent to modern multiyear droughts
duration longer than the several years to decade thereof
Seager et al., Journal of Climate, 2008

22. Can climate change disconnect the Great Lakes?

23. “Common sense holds that
what has really happened
can happen again.”
Vic Baker
University of Arizona

24. AP Photo/U.S. Coast Guard, Lt. Brendan Evans

26. “To anticipate future changes,
we must understand how and why
climates varied in the past.”
Ray Bradley
University of Massachuse s

27. CLIMATE FORCINGS El Niño during the Holocene

28. CLIMATE SIMULATIONS Climate reconstructions as model targets

29. GEOG5426 About me

33. (It was like this when we found it)

38. Pacific Decadal Oscillation index
3
2
1
0
-1
-2
-3
1900 1920 1940 1960 1980 2000

40. Office: 537 Social Sciences

41. GEOG5426 Nuts and bolts

42. Links to course syllabus, schedule
at h p://umn.edu/~stgeorge under ‘Teaching’

43. Course blog
h p://blog.lib.umn.edu/stgeorge/geog5426/

45. GEOG5426 Student opportunities
• Lead discussions throughout the semester
• Compose summaries of group discussions to
serve as shared resource on the course blog
• Research the climate history of a region of
your choice
• Summarize your findings in an AGU-style
presentation and a 10-page paper

47. GEOG5426 The plan for today

48. Ray Bradley University of Massachuse s

49. Neville Nicholls Monash University

50. GEOG5426 Today’s discussion
1. Ray Bradley provides two examples that illustrate the value
of a “Holocene perspective” on past drought. Which ideas in
these examples could only be obtained from paleo
evidence?
2. Neville Nicholls lists six reasons why climatologists study the
past. Are all these reasons valid for research that depends
on ‘natural’ archives? What is the difference between
‘modern’ and ‘past’ climates?

51. CLIMATE FORCINGS El Niño during the Holocene

52. Next week September 15, 2010
El Niño during the Holocene
• Historical archives
• Corals
• Tree rings