Feedbacks and Abrupt Climate Change

Review of last lecture

• Global climate models: Earth system models (5 components)

• Global climate models can reproduce the observed warming in the 20th century. The warming is largely caused by human activities.

• Projected change: mean temperature (largest warming over Arctic, larger over land), mean precipitation, sea level, extreme temperature, extreme precipitation, fresh water, ecosystems

• Future climate scenarios show that reducing greenhouse gas emissions can substantially mitigate warming in the latter half of this century.

Observed Change in Global Temperature: Significant warming

Global map of temperature change: Largest warming in Arctic (“Arctic amplification”)

Larger warming over land than ocean

Projected Change in Global Temperature: Significant warming

The spread comes from uncertainties in climate feedbacks

Main climate feedbacks for global warming

• Ice albedo• Temperature (Lapse rate)• Water vapor • Cloud• Aerosol• Carbon cycle

Ice albedo feedback – Arctic amplification

Water vapor feedback

Video: The climate wild card

• https://www.youtube.com/watch?v=Py1dEFKuJJU

Cloud feedback

Strongerwarming effect

Stronger cooling effect

Global carbon cycle

Carbon cycle feedback Example 1: Permafrost thaw

Carbon cycle feedback Example 2: Biosphere

Carbon cycle feedback sources

Video: A global warning?

• https://www.youtube.com/watch?v=_plr6bHo5j8

Projected Change in Global Temperature: Didn’t consider the abrupt change

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

Bifurcation and tipping point

Examples of tipping points

Summary

• Large spread in projected temperature change comes from uncertainties in climate feedbacks

• Main climate feedbacks for global warming: ice-albedo, temperature, water vapor, cloud, aerosol, carbon cycle

• Abrupt climate change and tipping points

Works cited• http://www.jpl.nasa.gov/images/earth/20100325/atlantic20100325-full

.jpg

• http://www.nasa.gov/centers/goddard/news/topstory/2004/0315humidity.html

• http://sitemaker.umich.edu/section2_group1/arctic_issues__permafrost

• http://www.all-creatures.org/hope/gw/02_Arctic-Antarctic.htm

• http://www.fedre.org/en/content/global-permafrost-zones-high-resolution-images-google-earth

• http://www.onlyzerocarbon.org/arctic_feedback.html

• https://www.marietta.edu/~biol/biomes/tropdry.htm

• http://www.nwf.org/Wildlife/Threats-to-Wildlife/Global-Warming/Global-Warming-is-Causing-Extreme-Weather/Wildfires.aspx

• http://www.opb.org/news/blog/ecotrope/qa-how-to-reduce-wildfire-severity-even-in-a-warmer-climate/