geog5426: class 1, course introduction

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: Rosa Say

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