Issues to be Considered:

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Paleoclimatology
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QUIZ!
On a scale of 0 - 10 The ozone hole and global
warming are related.
0 No way!
10You Betcha!
5 Coward
Last Updated July 13, 2015
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QUIZ!
On a scale of 0 - 10 We are currently in a cool
period of climate.
0 How quicklyyou forgetsummer.
10COOL!
5 Who knows?Ive got myair conditioneron!
Last Updated July 13, 2015
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Todays Issues
Driving Questions

1. How do we know that the composition of the
   atmosphere has changed in the past?
2. Ignoring greenhouse gas emissions what climate
   changes might we expect next?

Last Updated July 13, 2015
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Todays Issues
Climate has changed quite naturally over time
Last Updated July 13, 2015
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Todays Issues
Methods for establishing past temperatures

• Isotopic Geochemical Studies The study of rock
  isotopic ratios, ice core bubbles, etc.
• Dendochronology the study of tree rings
• Pollen Distribution the study of plant types and
  prevalence
• Lake Varves (like dendochronology, but with lake
  sediments)
• Coral Bed Rings
• Fossils Studies of geological settings, etc.
• Historical documents, paintings, etc.

Last Updated July 13, 2015
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Paleoclimatology
Isotropic Geochemical Studies
Heavy oxygen happens
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Paleoclimatology
Dating Through Oxygen Isotope Ratios
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Paleoclimatology
Dating Through Oxygen Isotope Ratios
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Paleoclimatology
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Vostok Record
d18O is well correlated with temperature!
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Sea Sediments
18O in sea sediments is used to suggest
temperature
Seawater 18O variations over time can be linked
to the growth and decay of ice sheets. During the
last ice age sea level was 130m lower than today
reflecting about 3 of the ocean's volume.
Consequently the 18O of the ocean was 1.2
permille heavier (higher) than it is today.
Measuring the 18O in foraminifera allows to
reconstruct past variations in the size of the
ice sheets over millions of years.
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Milankovitch theory of climate change
Eccentricity 400 ka and 100 ka
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Milankovitch theory of climate change
Obliquity 41 ka
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Milankovitch theory of climate change
Axial Precession 23 ka
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Paleoclimatology
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Milankovitch theory of climate change
Glacial
Ice Growth Configuration Low eccentricityLow
TiltLarge Earth-Sun Distance in Summer Net
Effect Less seasonal contrast
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Milankovitch theory of climate change
Inter-Glacial
Ice Growth Configuration High eccentricityHigh
TiltSmall Earth-Sun Distance in Summer Net
Effect More seasonal contrast
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Milankovitch theory of climate change
Take-away Variations in our orbit begin to
explain the variation in temperature over scales
of gt10,000 years.
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Paleoclimatology
Changes in CO2 (0 - 500,000,000 YBP)
Geochemically inferred.
NOW
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Paleoclimatology
Changes in CO2 (0 - 25,000,000 YBP)
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Paleoclimatology
Changes in CO2 (0 - 450,000 YBP)
NOW
Vostok
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Paleoclimatology
Changes in CO2 (0 - 450,000 YBP)
NOW
Vostok
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Lessons from Vostok
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Lessons from Vostok

1. Past changes in climate have often been triggered
   by changes in orbital characteristics.
2. These initial changes are then amplified by
   changes in CO2 and CH4 concentrations.
3. The changes in greenhouse gas concentrations then
   exaggerate the temperature changes over the earth.

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Paleoclimatology
Changes in CO2 (0 - 12,500 YBP)
NOW
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Climate
RAPIDChanges in Climate Happen
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RADIATION TEMPERATURE ICE VOLUME
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Paleoclimatology
Changes in CO2 (0 - 12,500 YBP)
NOW
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Paleoclimatology
Changes in CO2 (0 - 800 YBP)
NOW
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Paleoclimatology
Changes in CO2 (0 - 50 YBP)
NOW
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Summary
Driving Questions

1. How do we know that the composition of the
   atmosphere has changed in the past?

• Keywords
• Isotope Ratios
• Ice Cores

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Summary
Driving Questions

• Ignoring greenhouse gas emissions what climate
  changes might we expect next?

• Keywords
• Milankovitch Theory
• Eccentricity
• Precession
• Obliquity

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Paleoclimatology
Abrupt climate change (circa 2200 BC)forced the
abandonment of rain-fed settlements in
agricultural plains of lower Mesopotamia.
Abrupt extinction due to climate change
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Paleoclimatology
Period of drought between 800 to 1000 A.D.
probably contributed to collapse of Mayan
civilization.
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Paleoclimatology