This Week: Future Climate

1. This Week: Future Climate Future CO2 Forcing Climate Sensitivity – Feedbacks Natural Short and Long-term Forcings Global Warming Impacts

2. Announcements • See handout and website for details regarding paper and poster content • Poster Sessions: March 12 and 13 in Mary Gates Commons 10:30 – 11:20 • Monday March 17 8:30 AM, Final Exam, JHN 075 (here) • Papers and descriptions of 3 other posters due Wednesday March 19

3. Kaya Identity Model kaya identity model

4. Future Atmospheric CO2 One emission scenario Range of predictions suggest double pre-industrial by mid-century

5. Stabilization Scenarios 2100 2200 2300 2000 What our emissions can be for different constant CO2 levels. What do these tell us about future biosphere and ocean sinks?

6. Committed to Warming: Time Response

7. A Long View of Fossil Fuel Perturbation

8. Climate Sensitivity-All about Feedbacks T = F • is climate sensitivity parameter  units: K “per” W/m2  determined by feedbacks!

9. Estimates of Climate Sensitivity T change for a 4 W/m2 forcing (i.e. “double CO2”) Most probable  ~ 0.75 K/(W/m2)

10. Announcements • Get a handout on paper/poster guidelines • Brian’s office hours today canceled, moved to Thursday 5-6pm • My office hours are today, 3:30 – 4:30pm in 506 ATG

11. Feedbacks “feedback loop” +/- +/- State Variable Process or coupling Initial Forcing + increases state variable - decreases state variable

12. Ice-Albedo Feedback Albedo - Example of a positive feedback More solar radiation absorbed + Temperature + Initial Forcing (e.g. GHG) Ice melts, dark soils exposed

13. Water Vapor-Temperature Feedback Water Vapor + Increased Greenhouse effect + Temperature + Initial Forcing (e.g. GHG, solar radiation) More evaporation, saturation vapor pressure increase

14. Atmosphere—Protector of the Oceans? water trap If H2O reaches top of atmosphere it is blown apart by UV radiation H atoms escape to space, never to return Probable cause for no H2O on Venus

15. IR Flux-Temperature Feedback Outgoing IR flux increases + Example of a negative feedback - Temperature + Initial Forcing (e.g. GHG)

16. Phytoplankton-DMS-Marine Cloud Feedback Charlson, Lovelock, Andreae, Warren “C.L.A.W.” Hypothesis aerosols and cloudiness + - Solar Radiation (Temperature) Biogenic Sulfur Emissions + Initial Forcing (decreased clouds) + + Photosynthesis

17. Cloud Forcings and Feedbacks Low altitude thick clouds  Stratus High altitude thin ice clouds  Cirrus

18. Aircraft emit particles (and particle precursors) which can nucleat clouds. This activity gives rise to a • Positive radiative forcing • Negative radiative forcing

19. Aviation Contrails—Positive Forcing October 2004

20. Clouds and Climate—a complex problem Cirrus: Not so reflective, but absorb and emit at cold T Low Clouds: Absorb IR but emit like warm surface. Reflective

21. Clouds and Cloud Feedbacks Albedo + - Low Clouds + + Atmosphere holds more water Increased greenhouse effect + + High Clouds + Atmosphere holds more water Uncertain! Temperature Initial Forcing (e.g. GHG, solar radiation) Temperature

22. Predicted Changes in Cloud Forcings IPCC 2007

23. Sunspots – Cyclic Changes in Solar Output

24. ~11 year Sunspot Cycle

25. Radiative Forcing by Solar Cycle

26. The solar cycle forcing has increased from -0.1 to 0.2 W/m2 since 1900. This forcing can explain ____ of 1oC increase in global Avg. T since 1900 • 60 - 70% • 40 - 50% • 20 - 30%

27. False Assertions: Sun – Global Warming WRONG Solar Cycle WRONG T record Originally from WSJ Article written by two chemists named Robinson

28. False Assertions: Sun – Global Warming Correct cycle Laut 2003

29. T Response After Major Eruptions

30. Natural and Anthropogenic Forcings

31. El Nino Southern Oscillation-ENSO

32. Neutral Walker Circulation Neutral

33. El Nino/La Nina State Flip-Flop

34. El Nino/La Nina Circulation Patterns Very Strong El Nino Strong La Nina

35. ENSO “Periodicity” El Niño years La Niña years

36. El Nino Global Impacts

37. El Nino Impact on Fish Normal El Nino

38. Climate History

39. 18O Ratios in Sediment and Ice Core

40. Pleistocene Glacial and Interglacials Reconstruction of land and sea ice 21,000 years ago (last glacial maximum) February July

41. Records of NH Glaciations Geological Records: glacial deposits, scarring, larger scale Cordilleran Ice Sheet Lake Missoula Spokane Floods (from Lake Missoula)

42. Milankovitch—Before sediment cores Predicts glacial and interglacial transitions based on variations in Earth’s orbit His results suggested many such transitions in ~ 1 million yrs (he was right) —at the time, no observable records show that many, so his work widely criticized Milutin Milankovitch

43. Milankovitch Continued While lacking patience for critics, he did not lack confidence Milutin Milankovitch “I do not consider it my duty to give an elementary education to the ignorant, and I have also never tried to force others to use my theory, with which no one could find fault.”

44. Orbital Forcing Summary Precession Tilt Eccentricity IPCC 2007

45. Orbital Forcing Summary Cartoon • orbital forcings

46. Currently NH summer takes place at aphelion, in about 12,000 years, NH summer will occur at perihelion. At this time, SH seasonality will be • stronger • weaker

47. Solar Insolation at 65N and Glaciation

48. Recent UW Research Time rate of change of ice volume and solar insolation

49. The Key For Glaciation + Ice Coverage Solar insolation in NH summer appears to be key maintaining glaciation. Ice sensitive to melting! Positive Feedback—Destabilizing Climate - T Albedo - Initial Forcing Weaker NH summer insolation + Same old ice-albedo feedback, just different initial forcing

50. Questions—In Class Activity • Given the behavior of CO2 and CH4 is there a positive or negative feedback with T? • Provide a feedback involving marine biota which might explain CO2’s behavior. • Suppose marine biota are the cause of CO2’s behavior, is this support for or against Gaia theory? • When’s the next glacial maximum? Do you think we’ll get there?