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The Complexity of Global Climate Change

The Complexity of Global Climate Change. GLOBAL WARMING. 1. Introduction to the Greenhouse Effect On Earth On Other planets. 2. Global Warming Today? We need a record for comparison 3. Earth has a History of Climate Change Measuring climate change in Earth’s geologic past.

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The Complexity of Global Climate Change

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  1. The Complexity of Global Climate Change

  2. GLOBAL WARMING • 1. Introduction to the Greenhouse Effect • On Earth • On Other planets • 2. Global Warming Today? • We need a record for comparison • 3. Earth has a History of Climate Change • Measuring climate change in Earth’s geologic past. • Climate cycles in Earth’s past. • 4. Global Warming Today! • Why should we care? • Possible effects. • 5. Scientific Uncertainty • What’s Fact • What’s Probable • What’s Uncertain

  3. Introduction to the Greenhouse Effect • a. Greenhouse Gases – CO2, Water Vapor, etc. • b. Absorption of long wave radiation • c. Effects on Earth • d. Effects on other planets – Venus and Mars

  4. 2. How can we examine past climate? Isotopes – Varieties of an element that contain different #’s of neutrons Hydrogen Deuterium Tritium 0 neutrons 1 neutrons 2 neutrons Oxygen has several isotopes Isotope Atomic Mass Abundance 16O 15.99491463 99.7587% 17O 16.9991312 0.0374% 18O 17.9991603 0.2039%

  5. Seawater (H2O) has oxygen in it. Polar Ice is 30 p/mil Enriched in 16O Evaporation from oceans

  6. 3. Earth has a History of Climate Change • Measuring climate change in Earth’s geologic past. • Microfossil shells preserve ancient δO18 from seawater. • A record of past temperature CoccolithForaminifera

  7. 3. Earth has a History of Climate Change • Measuring climate change in Earth’s geologic past. • Paleothermometry with Oxygen Isotopes • Oxygen Isotopes – O16, O17, O18 • Ratio in Water Controlled by a. Temperature b. Phase Change (e.g., liquid to gas) • δO18 ~ O18/O16 • Cold Climate: δO18 in ocean • Warm Climate: δO18 in ocean

  8. 3. Earth has a History of Climate Change • The δO18 Record

  9. Other Sources of Climate Data a. Ice Cores – measure the amount of CO2 and other greenhouse gases in ice core bubbles.

  10. Other Sources of Climate Data b. Pollen – plant species are sensitive to climate.

  11. Other Sources of Climate Data c. Historical Records Winter Landscape by Peter Brueghel, 1601 The Little Ice Age in Holland

  12. 3. Earth has a History of Climate Change • Climate cycles in Earth’s past. • 1st Order – Hot House/Ice House: Millions of years

  13. 2. Earth has a History of Climate Change • Climate cycles in Earth’s past. • 2nd Order – Glacial/Interglacial: Thousands of years

  14. 2. Earth has a History of Climate Change • Climate cycles in Earth’s past. • 3rd Order – Years To Hundreds of Years: The Historical Record

  15. 2. Earth has a History of Climate Change • Why are there climate cycles? • Hypotheses - a. First Order: Changes in Greenhouse Effect from Plate Tectonics b. Second Order: Changes in amount and distribution of incoming solar radiation - Milankovitch Cycles c. Third Order – Sunspots, Volcanism, Other??

  16. 4. Global Warming Today? • Evidence for and against. • Atmospheric Rise in CO2

  17. Is The Earth Warming Up? • Evidence For: • 0.6o increase in global temperature • Sea-level rise of of 4-10” in last century • Growing season 11 days longer in N. hemisphere than in 1950’s. • Desertification of the Sahel (sub- saharan Africa). • Shrinking of Arctic Ice Pack

  18. Is The Earth Warming Up? • Evidence Against: • Computer models are inaccurate – predicted a 2o C rise in temperature. • Rise in temperatures inconsistent with CO2 input: T pre-1940; CO2 post- 1940. • Satellite measurements show no tropospheric warming. • Urban heat Island Effect.

  19. Is The Earth Warming Up? • Rebuttal to Against: • Computer models are not fortune tellers. Guides to understanding change and pointers to areas that need further study. • Rise in temperatures greatest in last decade. 1990’s were warmest decade of the millenium. • Satellite measurements are calibrated incorrectly? Lag time for temperature change to be recorded in atmosphere? • Urban heat Island Effect – Much better data now!

  20. Is The Earth Warming Up? Rebuttal to Against: GEOLOGIC DATA Shrinking of Arctic ice pack. Loss of tropical, high altitude glaciers. Melting of permafrost. Break-up of Antarctic ice shelves.

  21. 4. Scientific Uncertainty • What’s Fact a. The Greenhouse Effect is real and has operated throughout Earth History. b. Atmospheric concentrations of CO2 are increasing due to human activity. • What’s Probable a. 1 – 3o C Temp rise by 2150 b. Sea-level rise of 10 –30 cm • What’s Uncertain a. Effects on ocean/atmosphere circulation b. Weather Patterns c. Effects on Agriculture d. Runaway Greenhouse Effect?

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