Physical Science Basis of Climate Change : IPCC 2007

1. Physical Science Basis of Climate Change: IPCC 2007 Chapter 1. Historical Overview of Climate Change Science Jim Kinter 28 Jan 2010

2. 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

3. Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) E Planetary Emission In equilibrium, INCOMING ENERGY = OUTGOING ENERGY (1 - ) S  a2 = E (4  a2) E = 1/4 (1 - ) S Measured albedo () = 0.31 Calculated planetary E = 235 Wm-2 Measured planetary E = 237 Wm-2 Implied TE = 255 K (Stefan-Boltzmann)

4. 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

7. Hence the term, “Greenhouse Effect”

8. Earth’s Energy Balance Solar Radiation S = 1380 Wm-2 (plane, parallel) E 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 Calculated planetary E = 235 Wm-2 Measured planetary E = 237 Wm-2 Implied TE = 255K (Stefan-Boltzmann) Measured surface Es = 390 Wm-2 Atmosphere absorbs 153 Wm-2 Measured Ts = 288 K

9. What Factors Determine Earth’s Climate? 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

10. What Factors Determine Earth’s Climate? 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

11. What Factors Determine Earth’s Climate? 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.

12. 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.

13. What Factors Determine Earth’s Climate? 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

14. Electromagnetic Spectrum 255 K

15. The radiation absorption characteristics of water vapor 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 vapor (H2O) and carbon dioxide (CO2) are shown in the lower panels.

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

17. 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

18. 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 )

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

20. 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

21. Possible Origins of Climate Change

22. Progress inUnderstanding Climate Processes • Solar Variability and the Total Solar Irradiance • Measurement of the absolute value of total solar irradiance (TSI) • the changes in solar radiation could cause surface temperature changes of the order of a few tenths of a degree celsius. • After the invention of the telescope, the solar radiation variations can be inferred from cosmogenic isotopes (10Be, 14C) and from the sunspot number. • Measurements of TSI from mountain sites (Langley, 1884; Abbot, 1902-1957) • In 1978, the Nimbus-7 satellite was launched (Hickey et al., 1980) • The solar cycle variation in irradiance corresponds to an 10-11 year cycle in radiative forcing which varies by about 0.2 W m–2.

23. Measured range of variability

24. 2.5 W/m2 2.5 W/m2 = 0.2% 0.45 W/m2 0.45 W/m2 = 0.03% SOLAR OUTPUT VARIABILITY

25. Possible Origins of Climate Change

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

27. 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)

28. Possible Origins of Climate Change

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

30. 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)

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

32. Possible Origins of Climate Change

33. 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

35. Influence of volcanic plume on planetary albedo. (Source: Garrett, 1997)

36. Net solar radiation at Mauna Loa Observatory, relative to 1958 Climate Monitoring Division, NOAA

37. Reduction in global mean temperature following major volcanic eruptions BOM, Australia

38. What Factors Determine Earth’s Climate? • Change of global mean surface temperature • Warming • Greenhouse gases (GHG): Water vapor, carbon dioxide, methane • Human activities intensify the greenhouse effectthrough the release of GHG. • 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. • - Cloudscontribute locally to the greenhouse effect similar to that of GHG; however,clouds tend tohave a net cooling effect on climate.

40. Human activities contribute

42. Changes in Greenhouse Gases From Ice Age to Modern Data

43. What Factors Determine Earth’s Climate? 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

44. Nature of Earth Science • 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.

45. Nature of Earth Science • 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)

46. 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.

47. Figure 1.1

48. Nature of Earth Science • Self-correcting nature of Earth science: • Prediction of global cooling in the mid-1970s • - Global cooling over Northern Hemisphere (e.g., Gwynne,1975). • - Increases in carbon dioxide (CO2) should be associated with a decrease in global temperatures (Bryson and Dittberner, 1976) • - The cooling projected by their model was due to aerosols (small particles in the atmosphere) produced by the same combustion that caused the increase in CO2 (Bryson and Dittberner, 1977). • However, because aerosols remain in the atmosphere only a short time compared to CO2, the results were not applicable for long-term climate change projections.

49. Nature of Earth Science • Climate science in recent decades has been characterized by the increasing rate of advancement of research in the field and by the notable evolution of scientific methodology and tools, including the models and observations that support and enable the research. • Between 1965 and 1995, the number of articles published per year in atmospheric science journals tripled (Geerts, 1999). • Stanhill (2001) found that the climate change science literature grew approximately exponentially with a doubling time of 11 years for the period 1951 to 1997. • 95% of all the climate change science literature since 1834 was published after 1951. • The additional physics incorporated in climate models over the last several decades.

50. The complexity of climate models has increased over the last few decades. The additional physics incorporated in the models are shown pictorially by the different features of the modelled world. •  As aresult of the cumulative nature of science, climate science todayis an interdisciplinary synthesis of countless tested and provenphysical processes andprinciples painstakingly compiledand verified over several centuries of detailed laboratorymeasurements, observational experiments and theoreticalanalyses; and is now far morewide-ranging and physicallycomprehensive than was the case only a few decades ago. 1990 1996 2001 2007