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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.
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GEOG5426 Climate variations
Observations
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 MurphyElnora, Alberta
source: Globe and Mail, 1 July 2009
“
Examples of key instrumental climate records(from Bradley, 2008)
Central England temperature
Mean global temperatures
England and Wales precipitation
Southern Oscillation Index
Pacific Decadal Oscillation
Indian Monsoon
1659
1850
1766
1866
1900
1844
Climate history of North America
THOUSANDS OFYEARS AGO
0
MODERNOBSERVATIONS
LAST GLACIALMAXIMUM
20 16 48
YoungerDryas
Demise of LaurentideIce Sheet
Final Drainageof Lake Agassiz
12
CLIMATE PROXIESice cores
tree ringslake sediments
speleothemscorals
GEOG5426 Climate variationsHow 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?
Photograph: Heidi Barnett
TOOLS Paleolimnology and paleoecology
TOOLS Dendrochronology
TOOLS Ice cores
“Paleoclimatology reveals what has
actually happened.”
Jonathan OverpeckUniversity of Arizona
Did climate cause the failure of the Jamestown se"lement?
Did drought and disease affect the Spanish conquest of the Aztec?
“There is nothing magical about the last one hundred years.”
Balaji RajagopalanUniversity of Colorado
Photograph: Al_HikesAZ
Is the Colorado River over-allocated?
MEGADROUGHTintensity at least equivalent to modern multiyear droughts
duration longer than the several years to decade thereof
Seager et al., Journal of Climate, 2008
Can climate change disconnect the Great Lakes?
“Common sense holds that what has really happened
can happen again.”
Vic BakerUniversity of Arizona
AP Photo/U.S. Coast Guard, Lt. Brendan Evans
“To anticipate future changes, we must understand how and why
climates varied in the past.”Ray BradleyUniversity of Massachuse"s
CLIMATE FORCINGS El Niño during the Holocene
CLIMATE SIMULATIONS Climate reconstructions as model targets
GEOG5426 About me
(It was like this when we found it)
Pacific Decadal Oscillation index
1900 1920 1940 1960 1980 2000-3
-2
-1
0
1
2
3
Office: 537 Social Sciences
GEOG5426 Nuts and bolts
Links to course syllabus, scheduleat h"p://umn.edu/~stgeorge under ‘Teaching’
Course blogh"p://blog.lib.umn.edu/stgeorge/geog5426/
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
GEOG5426 The plan for today
Ray Bradley University of Massachuse"s
Neville Nicholls Monash University
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?
CLIMATE FORCINGS El Niño during the Holocene
Next week September 15, 2010
El Niño during the Holocene
• Historical archives
• Corals
• Tree rings
