SUBJECT AND CENTRAL QUESTION
Four Billion Years of Climate Change: Climate changed long before humans. Why? Examine orbital changes, solar output, volcanism, ice ages, paleoclimate proxies and CO₂..
RECOMMENDED VIEWING
Richard Alley, “The Biggest Control Knob: Carbon Dioxide in Earth's Climate History,” about 57 minutes. This is older—2009—but the basic paleoclimate physics remains excellent.
CLASS DISCUSSION
If climate has always changed naturally, why doesn't that explain the current warming? Does CO₂ lead temperature or follow it? Can both occur?
