Abrupt Climate Change

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Abrupt Climate Change
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Review of last lecture

• Large spread in projected temperature change
  comes from uncertainties in climate feedbacks
• Main climate feedbacks for global warming
  ice-albedo, temperature (lapse rate), water
  vapor, cloud, aerosol, carbon cycle

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Observing the atmosphere Proxy data(e.g. coral
reef, tree ring, lake sediment, ice core)

Coral reef
Tree ring
Lake sediment
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Ice core - The best proxy data for paleoclimate
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Ohio State Ice Core Group
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Ohio State Ice Core Sites
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Temperature during the past 2.4 billion years -
The ice ages
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What is an ice age?

• An ice age is a long interval of time (millions
  to tens of millions of years) when global
  temperatures are relatively cold and large areas
  of the Earth are covered by continental ice
  sheets and alpine glaciers.
• At least five major ice ages have occurred
  throughout Earths history. Currently, we are
  living in an ice age!
• Records show that ice ages typically develop
  slowly, whereas they end more abruptly.

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Extinction of mammoth
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Variations within an ice ageThe 100,000-year
glacial cycle
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Glacier distribution at the last glacial maximum
about 20,000 years ago
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Possible causes

• Change in atmospheric composition (e.g. CO2, CH4)
• Change in earths orbit (e.g. Milankovitch
  cycles)
• Motion of tectonic plates
• Change in solar output

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Abrupt climate change and tipping point Lesson
from Earths climate history
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Video A global warning?
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Termination of the Younger Dryas cold event and
last ice age 11,600 years ago
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Abrupt climate change and history/politics-
Collapse of Maya civilization and Chinese ancient
dynasties
Droughts
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The little ice age
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Pieter Bruegel the elder Winter landscape with
skaters and bird trap, 1565
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Bifurcation and tipping point
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Examples of tipping points
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Interactions among tipping points
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Summary

• Ice age a long time (millions to tens of
  millions of years) of cold temperatures and
  extended ice cover. gt5 in earths history
  (including now). Develop slowly, but end more
  abruptly.
• Glacial cycle has a 100,000 year oscillation
  period
• Past abrupt climate change
• Tipping points