1. What is the Greenhouse Effect?

2. Review of last lecture – What is energy? 3 methods of energy transfer – The names of the 6 wavelength categories in the electromagnetic radiation spectrum – The wavelength range of Sun (shortwave) and Earth (longwave) radition – The two basic motions of the Earth – What causes the four seasons: the 23.5 degree tilt of the Earth ’ s axis, and the 3 ways it affects the solar insolation (change of length of the day, beam spreading, beam depletion)

3. Satellite Measurements of the Earth’s Radiation Budget NASA ’ s Earth Radiation Budget Satellite (ERBS) 1985-1989

4. Earth’s energy budget (averaged over the whole globe and over a long time At the top of the atmosphere: At the top of the atmosphere: Incoming shortwave = Reflected Shortwave + Emitted longwave Incoming shortwave = Reflected Shortwave + Emitted longwave At the surface: At the surface: Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming) Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming) + Latent heat flux + sensible heat flux + Latent heat flux + sensible heat flux Sensible heat 7% Latent heat 23% Net Longwave 21% Yellow: shortwave Red: longwave

5. Atmospheric influences on radiation ReflectionScattering Absorption (absorber warms)

6. Atmospheric Absorption - The Greenhouse Effect Transparent to solar (shortwave) radiation Opaque to earth’s (longwave) radiation Major GH gases: CO 2, H 2 0 (v), CH 4

7. Recent change of greenhouse gases Global atmospheric concentrations of CO 2 and CH 4 have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice core measurements spanning the last 650,000 years! Global atmospheric concentrations of CO 2 and CH 4 have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice core measurements spanning the last 650,000 years! Deuterium (Temperature)

8. The importance of methane (CH 4 ) 23 times more powerful as a greenhouse gas than CO 2 23 times more powerful as a greenhouse gas than CO 2 The livestock sector is a major player, which accounts for 35-40% global anthropogenic emissions of methane (their burps!) The livestock sector is a major player, which accounts for 35-40% global anthropogenic emissions of methane (their burps!) The livestock sector is responsible for 18% of total greenhouse gas emissions The livestock sector is responsible for 18% of total greenhouse gas emissions Therefore, consuming less meat can help reducing global warming than not driving cars. Therefore, consuming less meat can help reducing global warming than not driving cars.

9. Video: The greenhouse effect http://www.youtube.com/watch?v=ZzCA60Wno Mk http://www.youtube.com/watch?v=ZzCA60Wno Mk http://www.youtube.com/watch?v=ZzCA60Wno Mk http://www.youtube.com/watch?v=ZzCA60Wno Mk

10. 3 Types of Scattering: 1.Raleigh 2.Mie 3.Non-Selective Atmospheric Scattering A discussion of each type follows…

11. involves gases smaller than insolation wavelength scatters light in all directions most effective at short wavelengths (violet, blue)… hence, blue sky Rayleigh Scattering The Earth has an atmosphere. So it has Rayleigh scattering and its sky appears blue The Moon has no atmosphere. So it has no Rayleigh scattering and its sky appears dark

12. Rayleigh scattering also explains reddish-orange sunsets when light travels through thick slice of atmosphere

13. Monet: Impressions, Sunrise

14. 2) Mie scattering –involves aerosols (e.g. dust, smoke) larger than gas molecules –forward scatter –equally effective across visible spectrum –explains hazy, gray days

15. 3) Non-selective scattering –Happens when atmospheric particles are much larger than the wavelength of incoming radiation (e.g. water droplets in clouds) –Act like lenses; scatter all wavelengths equally to create a white appearance –That ’ s why clouds appear white

16. Surface sensible and latent heat fluxes Both are turbulent (noisy) fluxes related to conduction and convection. Both are turbulent (noisy) fluxes related to conduction and convection. Both proportional to surface wind speed. Both proportional to surface wind speed. Sensible heat flux is dry flux from warm to cold regions Sensible heat flux is dry flux from warm to cold regions Latent heat flux (also called evaporation) is wet flux from wet to dry regions Latent heat flux (also called evaporation) is wet flux from wet to dry regions Important for hurricane amplification Important for hurricane amplification From NOAA ESRL Surface Wind

17. Summary: Earth’s energy budget At the top of the atmosphere: At the top of the atmosphere: Incoming shortwave = Reflected Shortwave + Emitted longwave Incoming shortwave = Reflected Shortwave + Emitted longwave At the surface: At the surface: Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming) Incoming shortwave = Reflected shortwave + Net emitted longwave (emitted - incoming) + Latent heat flux + sensible heat flux + Latent heat flux + sensible heat flux Sensible heat 7% Latent heat 23% Net Longwave 21% Yellow: shortwave Red: longwave

18. Summary Earth’s energy balance at the top of the atmosphere and at the surface. What percentage of solar energy is absorbed by the surface? Earth’s energy balance at the top of the atmosphere and at the surface. What percentage of solar energy is absorbed by the surface? Atmospheric influences on radiation (3 ways) Atmospheric influences on radiation (3 ways) What cause the greenhouse effect? What are the major greenhouse gases? Why is methane important? What cause the greenhouse effect? What are the major greenhouse gases? Why is methane important? The three types of atmospheric scattering. What causes the blue sky? Why causes the reddish-orange sunsets? The three types of atmospheric scattering. What causes the blue sky? Why causes the reddish-orange sunsets? Sensible heat flux (dry flux from warm to cold regions) and latent heat flux (wet flux from wet to dry regions). Both proportional to surface wind speed Sensible heat flux (dry flux from warm to cold regions) and latent heat flux (wet flux from wet to dry regions). Both proportional to surface wind speed