Physical Science Basis of Climate Change : IPCC 2007

1. Center of Ocean-Land-Atmosphere studies CLIM759: Topics in Climate Dynamics GEOG 670: Applied Climatology Physical Science Basis of Climate Change: IPCC 2007 Chapter 1. Historical Overview of Climate Change Science Emilia K. Jin Jan 29, 2008

2. Evaluation Criteria Center of Ocean-Land-Atmosphere studies • ◆ Oral presentation • - Group of 3-4 students will choose one topic among five topics. • Prepare a group presentation (60-70 min). • Either one or multiple speakers are good. • We are also welcome to add results based on other data, in particular your original research.

3. Evaluation Criteria Center of Ocean-Land-Atmosphere studies • ◆ Project paper • - Student will make a final paper individually focusing on observation and projection of global warming. • It is recommended that the topic of group presentation will be related with. • The results of your own original research based on IPCC report such as data analysis, modeling results should be included. • ◆ Examples of topics: Detection and Attribution • Analysis of observed data: Global warming trend in my hometown • Analysis of existing model output: Inconsistent results of IPCC climate change simulations for US summer mean temp. • Perform the model simulations: Modeling of global warming with different forcings • ….. • ◆ Deadline of project paper: 9 May 2008

4. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies • Climate: ‘Average weather’ • Change of climate system is cause by • 1) Internal Dynamics • 2) External Forcing: volcanic eruptions, solar variations, human-induced changes in atmospheric composition. • Solar radiation powers the climate system • 1) by changing the incoming solar radiation (e.g., by changes in Earth’s orbit or in the Sun itself) • 2) by changing the fraction of solar radiation that is reflected (called • ‘albedo’; e.g., by changes in cloud cover, atmospheric particles or • vegetation) • 3) by altering the longwave radiation from Earth back towards space (e.g., by changing greenhouse gas concentrations). •  Climate responds directly to such changes, as well as indirectly, through a variety of feedback mechanisms.

5. WHAT DETERMINES CLIMATE? • Energy balance at the top of the atmosphere • Determines the global average, annual average temperature at the top of the atmosphere • Affected by solar energy flux • Planetary albedo

6. Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) Planetary Emission In equilibrium, INCOMING ENERGY = OUTGOING ENERGY (1 - ) S  a2 = E (4  a2) E = 1/4 (1 - ) S Measured albedo () = 0.31 Measured planetary E = 237 Wm-2 Implied TE = 255 K

7. WHAT DETERMINES CLIMATE? • Energy balance at the top of the atmosphere • Determines the global average, annual average temperature at the top of the atmosphere • Affected by solar energy flux • Planetary albedo • Greenhouse effect • surface temperature of any planetary body with an absorbing/emitting atmosphere (e.g. Earth or Venus) is warmer than one without (e.g. Moon) • Surface temperature is therefore also affected by concentrations of absorber/emitter gases

10. Hence the term, “Greenhouse Effect”

11. Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) Planetary Emission Assume radiative equilibrium, so that INCOMING ENERGY = OUTGOING ENERGY (1 - ) S  a2 = E (4  a2) E = 1/4 (1 - ) S Measured albedo () = 0.31 Measured planetary E = 237 Wm-2 Implied TE = 255 K Measured surface Es = 390 Wm-2 Atmosphere absorbs 153 Wm-2 Measured Ts = 288 K

12. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies Global Radiative Balance  Heat and energy is transported from the equatorial areas to higher latitudes via atmospheric and oceanic circulations, including storm systems. BOM, Australia

13. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies Global Radiative Balance  Heat and energy is transported from the equatorial areas to higher latitudes via atmospheric and oceanic circulations, including storm systems. BOM, Australia

14. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies The pole-equator-pole radiation balance The poleward energy transport for the atmosphere and ocean This is necessary to achieve radiative balance. The zonal mean absorbed short wave and outgoing long wave radiation, as measured at the top of the atmosphere, are shown with their difference highlighted to show the excess in the tropics and the deficit at high latitudes. The lower part shows the required northward heat transport for balance (green), the estimated atmospheric transports (purple) and the ocean transports (blue) computed as a residual. BOM, Australia

15. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies Due to the rotation of the Earth, the atmospheric circulationpatterns tend to be more east-west than north-south. Embeddedin the mid-latitude westerly winds are large-scale weather systemsthat act to transport heat toward the poles. These weathersystems are the familiar migrating low- and high-pressure systems and their associated cold and warm fronts.

16. What Factors Determine Earth’s Climate? Because of land-oceantemperature contrasts and obstacles such as mountainranges and ice sheets, the circulation system’s planetary-scaleatmospheric waves tend to be geographically anchored by continentsand mountains although their amplitude can change withtime. Changes in various aspectsof the climate system - the size of ice sheets, the type anddistribution of vegetation or the temperature of the atmosphereor ocean - will influence the large-scale circulation features of theatmosphere and oceans.

17. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies Global mean surface temperature No atmosphere 239 102 341 239 239 T=255K “full” greenhouse effect 239 hypothetical atmosphere 102 341 239 478 239 T=303K Martens and Rotmans, CH2

18. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies Global mean surface temperature The natural greenhouse effect (TS-TO) depicted as the difference between the radiative equilibrium surface temperature of the atmosphere of preindustrial times (centre panel) and that of a hypothetical atmosphere with no radiatively active gases but the same albedo as at present (left panel). The right panel of the diagram shows schematically the radiative equilibrium temperature profile in the atmosphere resulting from the greenhouse effect compared with the planetary temperature of 255K. BOM, Australia

19. Center of Ocean-Land-Atmosphere studies Electromagnetic Spectrum 255 K

20. CH4 methane nitrous oxide N2O oxygen ozone O2 & O3 carbon dioxide CO2 water vapor H2O

21. The radiation absorption characteristics of water vapour and carbon dioxide as a function of wavelength. The upper portion of the chart shows the wavelength distribution of radiation emitted from black bodies radiating at 6000K (approximately the solar photosphere) and 255K (approximately the earth’s planetary temperature), with the solar irradiance measured at the mean distance of the earth from the sun. The percentage absorption of a vertical beam by representative atmospheric concentrations of water vapour (H2O) and carbon dioxide (CO2) are shown in the lower panels.

22. WHAT DETERMINES CLIMATE? • Energy balance at the top of the atmosphere • Determines the global average, annual average temperature at the top of the atmosphere • Affected by solar energy flux • Planetary albedo • Greenhouse effect • surface temperature of any planetary body with an absorbing/emitting atmosphere (e.g. Earth or Venus) is warmer than one without (e.g. Moon) • Surface temperature is therefore also affected by concentrations of absorber/emitter gases • Water vapor feedback changes in surface temperature produce (nonlinear) increases in water vapor thereby increasing the greenhouse effect • Instability and other feedbacks

23. Center of Ocean-Land-Atmosphere studies Water Vapor Feedback  H20 vapor • Absorb/emit IR Clausius – Clapyron Greenhouse Effect  Tsurf  Ftop = 4 Wm-2  Tsurf = + 1 K (without WVF )  Ftop = 4 Wm-2  Tsurf = + 2 K (with WVF )

24. FAQ 1.1, Figure 1 30% 100% 70% -19oC 20% 10% 14oC

25. Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) Planetary Emission Assume radiative equilibrium, so that INCOMING ENERGY = OUTGOING ENERGY (1 - ) S  a2 = E (4  a2) Terrestrial energy emission Solar energy flux Planetary albedo

26. Possible Origins of Climate Change

27. 2.5 W/m2 2.5 W/m2 = 0.2% 0.45 W/m2 0.45 W/m2 = 0.03% SOLAR OUTPUT VARIABILITY

28. Possible Origins of Climate Change

29. Energy Received From Sun Varies On Geologic Time Scales Earth orbit variability

30. Solar Radiation Received and Earth Orbital Parameters Time scale: 10s to 100s of millennia Total Insolation (solar radiation) Eccentricity (100 Kyrs) Obliquity (40 Kyrs) Precession (20 Kyrs)

31. Possible Origins of Climate Change

32. Global Thermohaline Ocean Circulation aka “Conveyor Belt” Time scale: Decades to centuries Article in Nature, 12/2/2005: Measurements indicate THC is slowing down

33. El Niño and the Southern Oscillation: the major mode of interannual variation in the tropical climate First simulated in a dynamical model by Philander and Seigel (Princeton, 1985)

34. El Niño years La Niña years Time scale: 4-7 years

35. Possible Origins of Climate Change

36. Radiative forcing (RF): the radiative imbalance (W m–2) in the climate system at the top of the atmosphere caused by the addition of a gas

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38. Center of Ocean-Land-Atmosphere studies Influence of volcanic plume on planetary albedo. (Source: Garrett, 1997)

39. Center of Ocean-Land-Atmosphere studies Net solar radiation at Mauna Loa Observatory, relative to 1958 Climate Monitoring Division, NOAA

40. Center of Ocean-Land-Atmosphere studies Reduction in global mean temperature following major volcanic eruptions BOM, Australia

41. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies • Change of global mean surface temperature • Warming • Greenhouse gases: Water vapour, carbon dioxide • Human activities intensify the blanketing effectthrough the release of greenhouse gases. • For instance, the amountof carbon dioxide in the atmosphere has increased by about 35%in the industrial era, and this increase is known to be due to humanactivities, primarily the combustion of fossil fuels and removalof forests. • - Cloudsdo exert a blanketingeffect similar to that of the greenhouse gases locally, even though clouds tend tohave a cooling effect on climate.

42. Center of Ocean-Land-Atmosphere studies Human activities contribute

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44. Center of Ocean-Land-Atmosphere studies Changes in Greenhouse Gases From Ice Age to Modern Data

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46. What Factors Determine Earth’s Climate? Center of Ocean-Land-Atmosphere studies Amplify (‘positive feedback’) or diminish (‘negative feedback’) the effects of a change in climate forcing. Example) Ice-Albedo feedback Greenhouse Gases Increase Warming Snow and Ice Melt More Sun’s heat Absorb Albedo Decrease Darker Surface

47. Nature of Earth Science Center of Ocean-Land-Atmosphere studies • Science is inherently self-correcting; • incorrect or incomplete scientific concepts ultimately do not survive repeated testing against observations of nature. • Each successful prediction adds to the weight of evidence supporting the theory, and any unsuccessful prediction demonstrates that the underlying theory is imperfect and requires improvement or abandonment. •  The IPCC assesses the scientific literature to create a report based on the best available science. •  The IPCC also contributes to science by identifying the key uncertainties and by stimulating and coordinating targeted research to answer important climate change questions.

48. Nature of Earth Science Center of Ocean-Land-Atmosphere studies • Earth scientists are unable to perform controlled experiments on the planet as a whole and then observe the results. • Sometimes a combination of observations and models can be used to test planetary-scale hypotheses. • Example 1) the global cooling and drying of the atmosphere observed after the eruption of Mt. Pinatubo provided key tests of particular aspects of global climate models (Hansen et al., 1992). • Example 2) Model projections was compared with observations (IPCC)

49. Center of Ocean-Land-Atmosphere studies Hansen et al., 1992 - Test the Aerosol Climate Forcing A: fast (exponential) growth rates for greenhouse gases and no volcanic aerosols after 1985. B: linear growth of greenhouse gases and an El Chichon sized volcano in 1995. El: Pinatubo aerosol properties are a 75• solution of sulfuric acid in water, with sizes based on the May and October distributions of Hofmann and Rosen (1983) 2*El: experiment r is twice as large as in the E1 experiment, in recognition of early reports that sulfur emissions from Pinatubo may have been twice as large as for E1Chichon. P: the same time dependence of global optical depth as the E1 and 2*El experiments, but with r 1.7 times larger than in E1 and the aerosol geographical distribution Modified.

50. Figure 1.1