1. Abrupt Climate Change

2. 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

3. Observing the atmosphere: Proxy data (e.g. coral reef, tree ring, lake sediment, ice core) Coral reefTree ring Lake sediment

4. Ice core - The best proxy data for paleoclimate

5. Ohio State Ice Core Group

6. Ohio State Ice Core Sites

7. Temperature during the past 2.4 billion years - The ice ages

8. 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.

9. Extinction of mammoth

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

11. Glacier distribution at the last glacial maximum about 20,000 years ago

12. Possible causes Change in atmospheric composition (e.g. CO 2, CH 4 ) Change in earth’s orbit (e.g. Milankovitch cycles) Motion of tectonic plates Change in solar output

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

14. Video: A global warning?

15. Termination of the Younger Dryas cold event and last ice age 11,600 years ago

16. Abrupt climate change and history/politics - Collapse of Maya civilization and Chinese ancient dynasties Droughts

17. The little ice age

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

19. Bifurcation and tipping point

20. Examples of tipping points

21. Interactions among tipping points

22. 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