Goldilocks Planet: Earth's Climate History
Warren Wiscombe
Earth is often called the Goldilocks Planet because its climate has been "just right" for life, with notable exceptions like mass extinctions. In this course, we will survey major milestones in the 4.5 billion year history of Earth's climate and how that climate has interacted with life. We will compare Earth with Venus and Mars and with the thousands of known exoplanets. In the end, we will understand why the Earth is indeed “the Goldilocks Planet”.
Note: This course does not deal with current climate, although it provides a lens through which to view it.
Week 1. Overview of a climate system.
Physical and chemical processes basic to climate. Planetary energy budget. Cycles of carbon and water. Climate forcing mechanisms. Climate feedbacks and response times.? Climate models: simple vs. complex; predictability vs. chaos; abrupt change and “tipping points”.
Week 2. Major milestones in Earth climate from 4.5 to 0.6 billion years ago: Hadean atmosphere and climate. Faint Young Sun paradox. Late Heavy Bombardment. Beginning of continents and plate tectonics. Beginning of life. Great Oxidation Event. The “Boring Billion”. Snowball Earths.
Week 3. Paleoclimate proxy data: Geologic periods. Layered records. Isotopes. Fossils. The role of greenhouse gases, aerosols, and clouds. Hothouse and Icehouse Earths. Probably causes of Paleocene-Eocene Thermal Maximum, the most recent hothouse.
Week 4. Mass extinctions, focusing on the Great Dying (Permian) and dinosaur (Cretaceous-Paleogene) extinctions. The role of super-volcanism in both extinctions. The story of how the asteroid-impact theory of dinosaur extinction changed geoscience forever.
Week 5. Ice Ages, focusing on the history of their discovery and the climate of the last 3 million years: The Great Ocean Conveyor Belt. The previous interglacial. Younger Dryas as prototype of rapid climate change. Heinrich Events.
Week 6. Life on Earth and its interaction with and possible control of climate (Gaia Hypothesis): How life survived extreme events. Extremophile life. History of oxygen and its role in creating multicellular life. The Cambrian Explosion of multicellular life forms. Astrobiology.
Warren Wiscombe, Ph.D has worked in the climate science field since the early 1970s, specializing in the interaction of radiation with the Earth’s atmosphere and surface. He worked for 30 years at NASA Goddard Space Flight Center, and before that in the Climate Section of the National Center for Atmospheric Research. He has taught climate and atmospheric science at New York University, NASA, University of Maryland, Weizmann Institute in Israel, and in Italy.
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