1. The importance of longevity in a greenhouse gas as climate forcing David Archer University of Chicago

3. Joseph Fourier Memoires d l’Academie Royale des Sciences de l’Institute de France VIIII, 570-604 (1827) Joseph Fourier described the greenhouse effect in 1827

4. T earth = 259 K = -14° C = 6°F Energy Balance of a Bare Rock

5. T atm = 259 K T earth = 303 K = 86° F A Planet with an Atmosphere

6. John Tyndall, 1859 John Tyndall discovered that CO 2, H 2 O, and CH 4 are greenhouse gases. O 2 and N 2 are not.

7. CO O Symmetric Stretch Asymmetric StretchBend CO O C O O COO Resting State No Resting DipoleIR Inactive 2349cm 660cm CO 2 is a greenhouse gas

8. Earth’s outgoing infrared spectrum

9. The band saturation effect

10. Radiative Forcing goes as ln(CO2)

11. Svante Arrhenius Svante Arrhenius calculated that doubling CO 2 would warm the Earth by 4-6°C, in 1896

12. The water vapor feedback Temperature + + Water Vapor Concentration Water Vapor Feedback

13. The Runaway Greenhouse Effect

14. Temperature + + Ice Melts Ice Albedo Feedbac The ice albedo feedback

15. David Keeling David Keeling started measuring CO 2 concentration in the atmosphere

16. The biosphere breathes

17. Various public predictions of detectable human-caused warming by year 2000 Charney report and others

20. Only greenhouse gas forcing looks like the recent temperature rise. Climate forcings Crowley, 2000

21. What about phenomena undreamed-of? The sun is good at pushing our climate buttons. Clouds? Humidity? “They blame CO 2 because they can’t think of anything else.”

22. A detective story The Butler. Found holding a smoking gun next to the deceased. Forensics matches the gun with the bullets. The Chauffer. In Kentucky for sister’s wedding. “Can’t think of any way he could have done it.” To convict the Chauffer, we’d have to first unconvict the Butler.

23. Airborne Fraction of Carbon Released Century timescale peak Millennial timescale tail Airborne fraction of fossil fuel CO 2

24. IPCC 2001 and earlier Summaries for Policymakers IPCC 2001 and earlier reports implied that global warming would last about a century.

25. Everyone gets this wrong Rutledge 2011 Ramanathan 2008 Shindell, 2012

26. Paleocene/Eocene Thermal Maximum Event 55 Myr Ago A natural release of CO 2, comparable to the potential fossil fuel release. Warming, with a recovery that took 100,000 years. Zachos et al. 2001

27. Long Tail Model Intercomparison Project LTMIP D. Archer, M.l Eby, V. Brovkin, A. Ridgwell, L. Cao, U. Mikolajewicz, K. Caldeira, K. Matsumoto, G. Munhoven, A. Montenegro, Ann. Rev. Earth Sciences, 2009.

28. 0 200 400 600 800 1000 1200 1600 1800 1400 0 1 2 3 4 5 6 0100300500 200 400 pCO 2 °C kyr Band saturation effect of IR absorbtion by CO 2 emphasizes the tail

29. CO 2 + CO 3 = + H 2 O 2 HCO 3 - 10100 2000  M CO 2 uptake capacity is determined by CO 3 = Seawater pH Chemistry Concentration in seawater

30. Atmosphere / Ocean Equilibrium 600 Gton C 1800 Gton C as CO 3 = Gton C = 10 15 g We expect a partitioning of ~1:3 between air and ocean

31. Atmosphere / Ocean Equilibrium Airborne Fraction of CO 2 Slug 1000-2000 Gton 4000-5000 Gton Archer 200522%33% Lenton 200621-26%34% CLIMBER22%35% Goodwin 200724-26%40% Ridgwell 200731%

32. Atmosphere / Ocean Equilibrium Affected by: changes in circulation biology ocean temperature saturating the carbonate ion buffer

33. Flakiness in ocean / atmosphere equilibrium

34. Neutralization by CaCO 3 CO 2 + CaCO 3 + H 2 O ==> Ca 2+ + 2 HCO 3 -

35. How long does it take? Neutralization e-folding timescale Archer 20055-8kyr Lenton 2006500 - 1000 yr Ridgwell 20071-2 kyr Tyrell 20072-3 kyr Pulls the airborne fraction down to ~ 10%

36. The Silicate Weathering CO 2 Thermostat CaSiO 2 -> Ca 2+ + SiO 2 Ca 2+ + CO 3 = -> CaCO 3 Burial + Subduction Weathering = function( CO 2 ) CaCO 3 + SiO 2 -> CaSiO 2 + CO 2 Volcanic CO 2 degassing

37. CO 2 >100,000 years The Silicate Weathering CO 2 Thermostat Helps explain Carl Sagan’s “Faint Young Sun” paradox

38. Time scale must be longer than this

39. Sea Level -150 -100 -50 50 100 5101520 Global Mean T, °C Sea Level, m Last Glacial Maximum 20kyr ago Eocene 40Myr ago Today Pliocene 3Myr ago IPCC Forecast Year 2100

40. Methane

41. Methane is about here CO 2 is here

42. Methane is about here CO 2 is here

43. Methane

45. Earth’s temperature response to radiative forcing Climate sensitivity:  T /  RF Time scale: 10 yrsUpper 100m Deep Ocean RF Thermal buffer of the deep ocean: Time scale 1000 yrs

47. Shindell, et al 2012

48. CO 2 vs. CH 4 CO 2 poses a “trap” for humanity, because of the time separation of the cause and the impacts, which will continue to worsen essentially forever. It’s like an ever-intensifying curse on our descendents, or planting a cancer. The climate impacts from CH 4 peak and subside within a human timescale. “Good” cholesterol vs. “Bad” cholesterol?

51. 1 Trillion tons of C => 2 °C peak warming Allen et al 2009

52. 1 Trillion tons of C Already released: 1/2 trillion tons 0.3 from fuels 0.2 from deforestation Costs (cuts / year) go up if we wait

53. Fossil fuels are mostly coal

54. Conclusions No one has a model or theory of climate that explains the present but predicts that global warming won’t happen and be significant. The impacts of global warming from CO 2 will last for millennia (not just a few centuries). The impacts of short-lived greenhouse gases is attenuated by the slow response time of Earth’s temperature. Lesson from the past: Sea level is 100x more sensitive to Earth’s temperature on thousand-plus year timescales than the forecast for the year 2100.