ES10 - EARTH

Lecture 19 Past (&Future) climates

Lisa Tauxe

Climate - what is it.

climate is the "average" of weather. it may be rainy today, but the climate of San Diego is sunny.

How do we read past climates

• direct measurement
• proxies:
• pollen
• tree rings
• corals
• oxygen isotopes
• fossils

How do we get the data

• Drilling:
• trees
• glaciers
• lakes
• oceans
• geological expeditions

Why does climate change?

• long-term:
• continental drift opens and closes seaways which changes oceanic circulation
• continental drift makes mountains, which change atmospheric circulation
• intermediate term:
• changes in earth's orbit affects climate
• short term:
• changing atmospheric chemistry from pollution
• volcanic dust

Past Climates - the study of paleoclimatology

• Cretaceous was ice free
• since about 50 million years ago, it's been getting colder.
• ice formed first on Antarctica (some 30 million years ago)
• northern hemisphere glaciation began only a few million years ago

the last few million years there have been repeated ICE AGES.

• Past glaciations - the late Pleistocene record

Future Climate

we don't know for sure what the climate will be, but we DO know that by burning fossil fuels, we are signifantly changing the chemistry of the atmosphere by adding large amounts of
carbon dioxide.

Carbon dioxide is a green house gas and could lead to a warmer climate in the future, with the attendant melting of the ice caps (resulting in flooding), warming of the equatorial ocean (resulting in more severe hurricanes), changes in precipitation (could be too wet or too dry), etc.

For more browsing pleasure, check out these links.

http://tvl1.geo.uc.edu/ice/glacier.html

http://mole.uvm.edu/whale/GlaciersGlacialAges.html

http://museum.state.il.us/exhibits/larson/glaciers.html

http://museum.state.il.us/exhibits/larson/environments.html

http://www.astr.ucl.ac.be/astr/en/research/paleoclimates/web/index.html

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