1. 1 MET 12 Global Climate Change - Lecture 9 Climate Models and the Future Shaun Tanner San Jose State University Outline  Current status  Scenarios  Global Models  Future Predictions

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5. 5 CO2, Methane, Nitrous Oxide

7. 7 Climate Change and humans  Anthropogenic increases in –greenhouse-gas concentrations –sulfate aerosols due to anthropogenic emissions  Emission scenarios have been developed  Changes in solar irradiance and volcanic aerosols –Unpredictable and difficult to model

8. Q: How do we predict what the future climate will be like? A: We use global models of the earth system 8

9. Sequence of Steps 1. Estimate future GHGs concentration 2.Using future GHG levels, calculate what future climate (e.g. temp, precip) will be like. 3.Assess the uncertainty of the predictions 9

10. Global Climate Modeling 1.Carbon cycle model 2.Global Climate Model 10

11. Figure 4.6 Main floor of the Earth Simulator Center in Yokohama, Japan

12. Figure 4.7 Elements of a global climate model

13. Figure 4.8 Genealogy of atmosphere GCMs

14. Figure 4.9 Examples of grid box systems

15. Figure 4.10 GCMs characterize fluxes into and out of a grid box during a time step

16. 16 Calculation of Future CO 2 Concentrations Carbon Cycle Model – Simulates atmosphere-biosphere and atmosphere-ocean interactions CO 2 Emissions -How much is going into atmosphere CO 2 Concentration - How much remains in atmosphere

17. 17 Carbon Cycle Models  Atmosphere/ocean and atmosphere/biosphere interactions not well understood  Model calculations contain uncertainty; the largest uncertainty: –Future uptake of carbon by the biosphere –Future uptake of carbon by the oceans

18.   – –   – – – –   – –   – – – – What factors affect future CO 2 levels? 18

19.  Global Population  Type of energy generation –Fossil intensive –Renewable energy  Growth of Economy  Type of Economy –Material based –Service and information based  Cooperation among countries –More homogeneous - share technologies –More isolated - larger divide between rich/poor countries What factors affect future CO 2 levels? 19

20. In 10 years, what do you expect you’ll earn annually? 1.Less than $20k 2.Between $20-40k 3.Between $40-60k 4.Between $60-80k 5.Between $80-100k 6.Between $100-150k 7.Over $150k

21. 21 What kind of car will you most likely purchase next? 1.SUV 2.Truck 3.Sportcar 4.Minivan 5.Station wagon 6.4 door sedan 7.Hybrid (gas/electric) 8.Electric

22. What best explains your eating patterns now? 1.Eat meat most meals 2.Eat meat a few times a week (3-5 times) 3.Eat meat occasionally (1-2 times per week) 4.Eat meat very occasionally (1-2 per month) 5.Vegetarian 6.Vegan

23. Scenarios (1) 23

24. 24 Scenarios (2)  A1 storyline –World of rapid economic growth –Population peaks 2050 –Different branches dependent on energy type/use  A1FI – Fossil intensive – continued dependence on coal/oil  A1T – Non-fossil intensive energy use (Technology)  A1B – Balance between fossil and non-fossil  A2 storyline –Heteorogenous world –technologies are not shared across borders, –population continues to increase

25. 25 Scenarios (3)  B1 storyline –Similar population as A1 –Global exchange/cooperation –Change in economic structures from product oriented to service oriented. –Focus on social and economic sustainability  B2 storyline –Population like A2 –Similar environmental and social focus –More regionally oriented (not as much exchange between countries).

26. Figure 4.16 Emissions scenarios (Part 1)

27. Figure 4.16 Emissions scenarios (Part 2)

28. Figure 4.18 Past and predicted changes in global average atmospheric CO 2 concentration

29. 29 Climate Model  A climate model is a mathematical representation of the physical processes that control climate –Basically everything that affects climate –Sun, atmosphere (greenhouse gases, aerosols), hydrosphere, land surface, cryosphere  Equations are very complicated –Some of the world’s largest supercomputers are running climate models

30. 30 Model Schematic Climate Model Changes in greenhouse-gas concentrations and changes in albedo due to aerosols Climate change (i.e. temperature, precipitation etc.)

31. 31 Model Verification: Can it be done?  Before you can trust any of these models, they must be verified. –We can use past climate as a test. If your model can simulate the past climate, then there is a reasonable chance that the model can accurately predict future climate.

32. 32 Can we predict changes in past climate?

33. Figure 4.29 Observed global temperature changes versus simulations via the HadGEM1 GCM

34. What conclusions can you infer from these model experiments? 1. 2. 34

35. 35 These experiments demonstrate that 1.The warming of the entire 20 th century is largely due to humans 2.The warming of the last 50 years is largely due to humans. 3.Natural factors are largely responsible for the warming of the 20 th century 4.Natural factors are not important in the early 20 th century, but more important in the last part of the 20 th century.

36. 36 Climate models 1.Are not useful for predicting the temperature changes observed during the 20 th century. 2.Show that volcanic eruptions and changes in sunlight are responsible for most of the changes observed over the 20 th century. 3.Can predict the 20 th century observed temperature changes with natural factors only. 4.Can only predict the 20 th century observed temperature changes when they include both human and natural contributions.

37. What conclusions can you infer from these model experiments? 1.Models can reasonably predict temperature variations over the last 150 years. 2.Most of the observed warming in the past 50 years is attributable to human activities. 37

38. Future Projections 38

39. 39 Carbon Emissions UNEP 2003

40. Figure SPM.5

41. Figure 4.34 Projected changes in surface temperatures comparing data (Part 2)

42. Figure 4.38 Projections of 21 GCMs about changes over the present century in precipitation

43. Figure 4.35 Past and future sea ice and sea level

44. 44 Future predictions: main changes in climate  Higher temperatures - especially on land –Arctic shows the largest warming  Hydrological cycle more intense –More rain overall  Sea levels rise –Why?  Changes at regional level –hard to predict  More intense weather (extremes) –Floods, droughts etc.

45. 45 Activity 4 1.Based on the A2 scenario, what is the predicted CO 2 concentration, temperature change and sea level change in 2100? 2.Based on the B1 scenario, what is the predicted CO 2 concentration, temperature change and sea level change in 2100? 3.Explain the differences.

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47. 47  Therefore, stabilizing emissions is not enough to reduce the radiative forcing  Based on above, how much will emissions have to decline in % to stabilize CO2 at 550ppm?

48. Mean Temperature (2050): relative to 1961-90 A1FI is A, B or C? B2 is A, B or C? A B C 48

49. 49 Indicate the correct matching 1.A1FI – A, B2 - B 2.A1FI – B, B2 – A 3.A1FI – C, B2 – A 4.A1FI – A, B2 – C 5.A1FI – B, B2 - C 6.A1FI – C, B2 – B

50. Mean Temperature (2050): relative to 1961-90 A1F A2 B2 50

51. 51 A B C Constant Aerosols ____ Increasing aerosols____ Decreasing aerosols____

52. The correct order of the graph is (Constant, Increasing Aerosols and Decreasing Aerosols) 1.A B C 2.A C B 3.B A C 4.B C A 5.C A B 6.C B A 52

53. 53 A B C Constant Aerosols Increasing aerosols Decreasing aerosols

54. 54 If CO 2 emissions were stabilized at present day values, CO 2 concentrations would 1.Continue to increase 2.Stabilize 3.Start to decrease