Abrupt Climate Change

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

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

core)

Coral reef Tree ring

Lake sediment

Ice core - The best proxy data for paleoclimate

Ohio State Ice Core Group

Ohio State Ice Core Sites

Temperature during the past 2.4 billion years - The ice ages

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 Earth’s history. Currently, we are living in an ice age!

• Records show that ice ages typically develop slowly, whereas they end more abruptly.

Extinction of mammoth

Variations within an ice age:The 100,000-year glacial cycle

Glacier distribution at the last glacial maximum about 20,000

years ago

Possible causes

• Change in atmospheric composition (e.g. CO2, CH4)

• Change in earth’s orbit (e.g. Milankovitch cycles)

• Motion of tectonic plates• Change in solar output

Abrupt climate change and tipping point– Lesson from Earth’s climate history

Video: A global warning?

Termination of the Younger Dryas cold event and last ice age 11,600

years ago

Abrupt climate change and history/politics

- Collapse of Maya civilization and Chinese ancient dynasties

Droughts

The little ice age

Pieter Bruegel the elder: Winter landscape with skaters and bird trap, 1565

Bifurcation and tipping point

Examples of tipping points

Interactions among tipping points

Summary• Ice age: a long time (millions to tens of millions of years)

of cold temperatures and extended ice cover. >5 in earth’s history (including now). Develop slowly, but end more abruptly.

• Glacial cycle: has a 100,000 year oscillation period

• Past abrupt climate change

• Tipping points