1. JTH14 1 The Modeling of Climate and Climate Change; can we trust model predictions? University of California, Irvine 21 February 2003 by John Houghton

2. JTH15 2 Outline Introduction Cloud Radiation Feedback Ocean Interactions The Carbon Cycle The Climate of the 20th Century Climate Projections for the 21st Century Regional Climate Modeling Patterns of Climate Response

3. JTH15 3 The greenhouse effect Long-wave radiation 236 Wm -2 Equivalent T = 255 K (-18ºC) 390 Wm -2 T = 255 K (-15ºC) 236 Wm -2 Solar radiation

4. JTH15 4 Spectra of outgoing radiation from Earth observed by IRIS on Nimbus 3

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6. JTH15 6 The Enhanced Greenhouse Effect Solar (S) and longwave (L) radiation in Wm  2 at the top of the atmosphere SL236 T =  18°C SL 236232 CO 2 x 2 SL236 CO 2 x 2 SL236 CO 2 x 2 + Feedbacks H 2 O (+60%) Ice/Albedo (+20%) Cloud? Ocean? T S = 15°C  T S ~ 1.2K  T S ~ 2.5K

7. JTH15 7 The climate system

8. JTH15 8 The Development of Climate models, Past, Present and Future Atmosphere Land surface Ocean & sea-ice Sulphate aerosol Sulphate aerosol Sulphate aerosol Non-sulphate aerosol Non-sulphate aerosol Carbon cycle Atmospheric chemistry Ocean & sea-ice model Sulphur cycle model Non-sulphate aerosols Carbon cycle model Land carbon cycle model Ocean carbon cycle model Atmospheric chemistry Atmospheric chemistry Off-line model development Strengthening colours denote improvements in models Mid 1970s Mid 1980sEarly 1990sLate 1990sPresent dayEarly 2000s?

9. JTH15 9 Predicting impacts of climate change Emissions Concentrations CO 2, methane, sulphates, etc. Global climate change Temperature, rainfall, sea level, etc. Regional detail Mountain effects, islands, extreme weather, etc. Impacts Flooding, food supply, etc. Scenarios from population, energy, economics models Carbon cycle and chemistry models Coupled global climate models Regional climate models Impacts models The main stages required to provide climate change scenarios for assessing the impacts of climate change. Hadley Centre - PRECIS brochure

10. JTH15 10 Coupled atmosphere / ocean climate model Radiation Atmosphere: Density Motion Water Heat Exchange of: Momentum Water Ocean: Density (inc. Salinity) Motion Sea Ice Land

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12. JTH15 12 19 levels in atmosphere 20 levels in ocean 2.5 lat 3.75 long 1.25 THE HADLEY CENTRE THIRD COUPLED MODEL - HadCM3 30km -5km

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14. JTH15 14 Physical Feedbacks Water vapour Ice albedo Clouds Oceans Ice sheets

15. JTH14 15 Cloud Radiation Feedback

16. JTH15 16 Cloud radiation feedback

17. Global average change in T /C

18. JTH15 18 Model Estimates of Cloud Radiative Forcing with CO 2 Doubling

19. JTH15 19 Effect of cloud feedback formulation on climate prediction Feedback schemeGlobal Av Temp change,C for doubled CO2 –RH5.3 –CW2.8 –CWRP1.9 –after Senior & Mitchell, Hadley Centre

20. JTH15 20 Net cloud forcing: January to July Hadley Centre

21. JTH15 21 SHIP TRACKS UNDER CLOUD Washington state

22. JTH14 22 Ocean Interactions

23. JTH14 23 IPCC Synthesis Report

24. JTH15 24 Strength of the thermohaline circulation in the North Atlantic. Hadley Centre

25. JTH15 25 IPCC Third Assessment Report Modelled transport of water in Atlantic conveyor belt

26. JTH15 26 Projected changes in annual temperatures for the 2050s The projected change in annual temperatures for the 2050s compared with the present day, when the climate model is driven with an increase in greenhouse gas concentrations equivalent to about 1% increase per year in CO 2 The MetOffice. Hadley Center for Climate Prediction and Research. BW 11

27. JTH15 27 Changes in surface air temperature, relative to the present day, 20 years after the hypothetical collapse of the thermohaline circulation. Hadley Centre

28. JTH15 28 Surface Temperature Combined effect of THC collapse (2049-2059) and global warming Cooling over UK: 1-3°C

29. JTH14 29 The Carbon Cycle

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31. JTH15 31 IPCC Third Assessment Report

32. JTH15 32 Human Perturbation of the Carbon Cycle

33. JTH15 33 Partitioning of CO 2 uptake using O 2 measurements

34. JTH15 34 1980s 1990s Atmospheric increase 3.3 ± 0.1 3.2 ± 0.1 Emissions (fossil fuel, cement) 5.4 ± 0.3 6.3 ± 0.4 Ocean-atmosphere flux -1.9 ± 0.6 -1.7 ± 0.5 Land atmosphere flux -0.2 ± 0.7 -1.4 ± 0.7 partitioned as follows: Land-use change 1.7 (0.6 to 2.5) NA Residual terrestrial sink -1.9 (-3.8 to 0.3) NA IPCC Third Assessment Report Global CO 2 budgets in GtC per year

35. JTH15 35 Carbon cycle feedbacks

36. JTH15 36 Change in carbon content of soil (top) and vegetation (bottom) between 1860 and 2100 - predicted by Hadley Centre climate model Hadley Centre

37. JTH15 37 Simulated changes in the global total soil and vegetation carbon content (Gt C) between 1860 and 2100. Hadley Centre

38. JTH15 38 Influence of ENSO on CO 2 Variability Annual changes in atmospheric CO 2 are dominated by ENSO –after removing anthropogenic rise –rise during El Nino –fall during La Nina  CO 2 - black, Nino3 - red

39. JTH15 39 Influence of Volcanoes on CO 2 Variability 2 notable exceptions to ENSO correlation CO 2 levels lower than expected Coincide with major volcanic eruptions  CO 2 - black, Nino3 - red El Chichon Pinatubo

40. JTH15 40 Constraint from ENSO Sensitivity Model with q 10 =2 has realistic sensitivity to ENSO. Reconstructions for range of q 10. Infer q 10 =2.1±0.7.

41. JTH15 41 Constraint from Sensitivity to Volcanoes Model with q 10 =2 has realistic sensitivity to Pinatubo. Reconstructions for range of q 10. Infer q 10 =1.9±0.4

42. JTH15 42 ENSO and Pinatubo Variations as a constraint on climate-carbon cycle feedback Model without C cycle Feedback Model with C cycle Feedback (q 10 = 2) Grey region is estimate of uncertainty related to q 10 parameter for soil respiration q 10 = 3 q 10 = 1

43. JTH15 43 Photo: Tim Hewison

44. JTH15 44 Estimated carbon uptake if suitable arable land north of 30º N were to be replaced with trees. Hadley Centre The additional effect on climate of the changes in surface reflectivity when trees are planted on suitable arable land north of 30º N, expressed as equivalent carbon emissions. The difference between the two diagrams above. Negative values show where the net effect of planting trees is to warm climate.

45. JTH15 45 NET EFFECT OF PLANTING TREES expressed as equivalent carbon uptake tonnes of carbon per hectare –500 100150200 Negative values show where the net effect of planting trees is to warm climate Met Office / Hadley Centre

46. JTH15 46 EMISSIONS AND CONCENTRATIONS OF CO 2 from unmitigated and stabilising emission scenarios Unmitigated emissions 750 ppm stabilisation550 ppm stabilisation Source: IPCC

47. JTH15 47 The Climate of the 20 th Century

48. JTH15 48 Global mean surface air temperature anomalies from 1,000 year control simulations with three different climate models, - Hadley, GFDL and Hamburg, compared to the recent instrumental record. No model control simulation shows a trend in surface air temperature as large as the observed trend. If internal variability is correct in these models, the recent warming is likely not due to variability produced within the climate system alone. IPCC Third Assessment Report

49. JTH15 49 Simulated annual global mean surface temperatures Natural forcing Anthropogenic forcing

50. JTH15 50 Simulated annual global mean surface temperatures

51. JTH15 51 IPCC statements on Detection “The balance of evidence suggests a discernible human influence on global climate” 1995 Report “There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities”2001 Report

52. JTH14 52 Climate Projections for the 21st century

53. JTH15 53 The solid line shows a GCM prediction of temperature change. Prior to 1990, historical emissions were used. Beyond 1990, the IS92a emissions scenario was used. The dashed line shows the results of scaling the model prediction to give the best fit to the most recent 50 years of observations. The shaded region is the uncertainty estimate. Hadley Centre

54. JTH15 54 SRES scenario familys More economic More environmental More regional More global B: balanced FI: fossil intensive T: non-fossil A1 A2 B2B1

55. JTH15 55 IPCC Third Assessment Report Globally averaged tempertaure change for scenario SRES B2

56. JTH15 56 IPCC Third Assessment Report Globally averaged precipitation change for scenario SRES B2

57. JTH15 57 Hadley Centre - PRECIS brochure Area averaged changes in summer rainfall for the period 2071-2100 over southern Asia as predicted by nine coupled models forced by the A2 emissions scenario (taken from Chapter 10 of the Scientific Basis of the IPCC Third Assessment Report). In other areas predictions can show much greater differences in magnitude and even sign.

58. JTH15 58 Observed and projected changes in extremes Confidence in observed changes (latter half of the 20th century) Likely Very likely Likely, over many areas Likely, over many Northern Hemisphere mid- to high- latitude land areas Likely, in a few areas Not observed in the few analyses available Insufficient data for assessment Changes in Phenomenon Higher maximum temperatures and more hot days over nearly all land areas Higher minimum temperatures, fewer cold days and frost days over nearly all land areas Reduced diurnal temperature range over most land areas Increase of heat index over land areas More intense precipitation events Increased summer continental drying and associated risk of drought Increase in tropical cyclone peak wind intensities Increase in tropical cyclone mean and peak precipitation intensities Confidence in projected changes (during the 21st century) Very likely Very likely, over most areas Very likely, over many areas Likely, over most mid-latitude continental interiors (Lack of consistent projections in other areas) Likely, over some areas IPCC Third Assessment Report

59. JTH15 59 Simulated temperature rise and thermal expansion for the 4xCO2 experiment

60. JTH14 60 Regional Climate Modelling

61. JTH15 61 Hadley Centre - PRECIS brochure Schematic diagram of the resolution of the Earth’s surface and the atmosphere in the Hadley Centre regional climate model.

62. JTH15 62 Regional Climate Model High resolution (50km) over limited area (Europe, Indian subcontinent) Embedded in global model, so subject to same uncertainties Takes account of local characteristics, e.g. mountains, coasts Better regional detail, better prediction of extremes in weather (eg flooding) Everybody wants one!

63. JTH15 63 Hadley Centre - PRECIS brochure The representation of the Philippines in RCMs with resolutions of 400 km (the GCM), 50 km and 25 km.

64. JTH15 64 Hadley Centre - PRECIS brochure Patterns of present-day winter precipitation over Britain. Left, as simulated with the global model. Middle: as simulated with the 50 km regional model. Right, as observed.

65. JTH15 65 Hadley Centre - PRECIS brochure The frequency of winter days over the Alps with different daily rainfall thresholds. Purple bars, observed. Dark red bars simulated by the GCM. Green bars simulated by the RCM.

66. JTH15 66 Hadley Centre - PRECIS brochure A tropical cyclone is evident in the mean sea-level pressure field from the RCM (right) but not in the driving GCM (left) for the corresponding day (from an RCM over southern Africa, developed by the Hadley Centre in collaboration with the university of Cape Town).

67. JTH15 67 Hadley Centre - PRECIS brochure Predicted changes in summer surface air temperatures between the present day and the end of the 21st century. Left, from the global model. Right, from the regional model.

68. JTH15 68 Hadley Centre - PRECIS brochure Predicted changes in monsoon precipitation over India, between the present day and the middle of the 21st century from the GCM (left) and the RCM (right).

69. JTH14 69 Is the Climate Chaotic?