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VII. Climate Change Blackbody model Windows and saturation Feedbacks Aerosols

VII. Climate Change Blackbody model Windows and saturation Feedbacks Aerosols. Blackbody model. Energy In = Energy Out Energy In = 1368 W/m 2  Earth cross-section  (1-reflectivity) Energy Out = Earth surface Area  s SB  T earth 4 s SB is Stefan-Boltzmann constant

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VII. Climate Change Blackbody model Windows and saturation Feedbacks Aerosols

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  1. VII. Climate Change Blackbody modelWindows and saturationFeedbacksAerosols

  2. Blackbody model Energy In = Energy Out Energy In = 1368 W/m2  Earth cross-section  (1-reflectivity) Energy Out = Earth surface Area  sSB Tearth4 sSB is Stefan-Boltzmann constant Tearth = 255 K ignores clouds and greenhouse gases

  3. Energy Balance beyond Blackbody

  4. Earth’s IR Emissions

  5. Energy Balance beyond Blackbody

  6. CO2 Concentration increasing, seasonal variation Absorptions are nearly saturated

  7. Strong CO2 absorptions almost saturated. Window regions between strong absorbances: Activity: model greenhouse gases X and Y a) Consider [Y] = 2.5 x 1013 molecules cm-3 at l1 in IR, sY = 1 x 10-19 cm2 molecule-1 What is A(l1), the absorbance at l1 ? b) Add [X] = 2.5 x 1011 molecules cm-3 at l1 in IR, sX = 4 x 10-18 cm2 molecule-1 at l2 in IR, sX = 1 x 10-18 cm2 molecule-1 What is the total A(l1) and what is A(l2)? c) Does the addition of X reduce heat emission more at l1 or l2? Saturation

  8. Human Affects on Radiation Budget Global mean radiative forcing of climatefor year 2000 relative to 1750 (IPCC)

  9. Greenhouse Gases See Coursepack Section E Table 3 Seinfeld and Pandis Figures 21.17-19 Instantaneouse Radiative Forcing (IRF) of a compound (Watts m-2 kg-1) Absolute Global Warming Potential (W m-2 kg-1 yr)

  10. Greenhouse Gases Global Warming Potential (w/respect to CO2) (dimensionless)

  11. Key Points • Radiative balance is complicated • Greenhouse Gas effect real, global • Greenhouse Gas effects not isolated • - feedbacks with biosphere • - feedback with geosphere • Aerosol effects messy, local (temporary) • Climatic effects hard to see (weather)

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