Global Warming:

1. Global Warming: From Science to Policy

2. Outline Science History Evidence Theory Simulations Politics Policy Choices and Options

3. Science

4. History Why is the Earth Warm? John Tyndall (1862) Ice Ages Modeling the Earth Most Gases are Transparent in the IR But: CO2 and Water Vapor Completely Opaque at 1 part in 10,000. Arhennius (1896) CO2- Water Feedback Manmade inputs Snowball Earths (1930s)

5. History

6. History “Fatal” Objections Human Colonization of North America CO2 Spectra Saturated Seawater Chemistry

7. History New Evidence CO2 Theory CO2 Evidence (1930s to 1960s) Roger Revelle Computer Models of the Oceans and Atmosphere (1960s)

8. History

9. History New Evidence, ctd… Pollen, Isotopes, Ice Data show abrupt swings in climate (1960s – present). What We Still Don’t Know Milankovich Terms

10. Evidence The Principal Evidence CO2 Temperature Data

11. CO2 Records … a sixteen-fold increase!

12. CO2 Records

13. CO2 Records

14. Temperature: The (Very) Long View

15. 3 Million Years 5o Note: Time-Reversed! Onset of Ice Ages

16. 420,000 Years 5o Ice Ages Dominate Recorded History is An “Interglacial”

17. 100,000 Years 5o Recorded History is Anomalously Warm, Stable Actual Global Warming is Small on This Plot Claim: Global Warming Could Be Comparable

18. Sudden Swings

19. 10,000 Years 5o Fluctuations on All Scales End of Last Ice Age - Abruptness

20. 2,500 Years Fluctuations on All Scales 700 Year Dip Prior to 20th Century 5o

21. 20th Century 1/2o Cooling from 1940 to 1970 Recent Warming Looks Real

22. Intuition: Our climate is … changeable anomolous unstable getting warmer

23. Theory Well-Behaved Theories Solvable Theories Perturbation Methods Feedback Complexity An Interdisciplinary Subject Astronomy, biology, chemistry, physics, meteorology, oceanography, etc.

24. Theory

25. Theory

26. Theory

27. Theory Feedbacks: Clouds, dust, soot, aerosols, sunspots, cosmic rays?

28. Theory

29. Simulations The Third Branch of Science The Physical Intuition Problem Predicting the Past Convergence Deciding Which Model is Right

30. Simulations

31. Simulations

32. Taking Stock

33. “By the late 1980s, well-informed people understood that the climate change issue could not be handled in either of the two easiest ways. Scientists were not going to prove that there was nothing to worry about. Nor were they about to prove exactly how climate would change, and tell what should be done about it.” [160] Spencer Weart The Discovery of Global Warming (2003) http:www.aip.org/history/climate

34. “When the [IPCC] announced in 2001 that they found it “likely” that the current unprecedented rate of warming was largely due to the rise of greenhouse gases, they explained in a footnote what ‘likely” meant: they judged the probability that the finding was true lay between 66 and 90 percent.” Spencer Weart The Discovery of Global Warming (2003) http:www.aip.org/history/climate

35. Technology Options Cutting Back Carbon Sinks USA – East Coast – 0.5 Pg/yr vs. 5.4Pg/yr worldwide emissions Tropics – Deforestation – 1.7 Pg/yr

36. Technology Options Geoengineering Solutions Seeding The Ocean, Making Smog, Carpeting Nevada? Nuclear Power Fusion

37. Politics

38. Politics Kyoto Rollback to 92% of 1990 Levels Not Enough! Tradable Credits Does Not Include LDCs US Senate Rejection Russia

39. Politics Gore, Singer & Revelle NAS Committee Reports The Hockey Stick Dispute LDCs and Kyoto Russia and Kyoto

40. Policy

41. The Cost Gradual Effects: 450 ppm 1.2 – 2.3 C increase by 2101 550 ppm 1.5 – 2.9 C increase by 2101 650 ppm 3.2 C Abrupt Effects: Antarctic Glacier Collapse Collapse of Ocean Circulation How Important? Local? Entering A New Climate Mode How Distant? One century or fifty?

42. Distribution Issues Russia Bangladesh North-South

43. Timing To first approximation, emissions stay in atmosphere. Paths need to approach 0 on a roughly 100 year time scale IGPCC Proposals: Go from 380 ppm to 550 in 2050 and stabilize. Caldiera et al, “Climate Sensitivity Uncertainty and the Need for Energy Without CO2 Emission,” Science299:2052 (2003)

44. What Will It Cost? US estimates range from less than 1% to 4% of GDP.

45. Timing Waiting for Technology Waiting for Depreciation

46. Timing Matters Human Health and Happiness

47. How Much Risk? Total Emissions Depends on Climate Model Caldiera et al, “Climate Sensitivity Uncertainty and the Need for Energy Without CO2 Emission,” Science299:2052 (2003)

48. How Much Risk? Investment in new primary power sources depends on climate models Caldiera et al, “Climate Sensitivity Uncertainty and the Need for Energy Without CO2 Emission,” Science299:2052 (2003)

49. How Much Risk? Investment in new generating capacity depends on climate models 400 MW/day was replaced during the 1990s (10% renewable) Caldiera et al, “Climate Sensitivity Uncertainty and the Need for Energy Without CO2 Emission,” Science299:2052 (2003)

50. How Much Risk? Making Large Bets The Precautionary Principle Option Value Should We Wait for Better Data?