1. Recent Climate, Energy Balance and the Greenhouse Effect David B. Reusch Penn State/New Mexico Tech dreusch@ees.nmt.edu CVEEN 7920/Geol 571

3. ~4 x 10 26 W W = watts = power = energy/sec

4. ~4 x 10 26 W W = watts = power = energy/sec

5. ~4 x 10 26 W W = watts = power = energy/sec

6. Basic Balance  342 W/m 2 of shortwave radiation input from the Sun is balanced by…  Earth outputs totaling 342 W/m 2 of  Reflected/scattered shortwave  Absorbed/re-emitted longwave  So what temperature is that?  342 W/m 2 of shortwave radiation input from the Sun is balanced by…  Earth outputs totaling 342 W/m 2 of  Reflected/scattered shortwave  Absorbed/re-emitted longwave  So what temperature is that?

7. Earth’s Average Temperature  An input of 342 W/m 2 translates to a mean surface temperature of -18 °C  We know that T A is actually 15 °C so what’s missing?  The short answer: an atmosphere which provides the natural greenhouse effect  An input of 342 W/m 2 translates to a mean surface temperature of -18 °C  We know that T A is actually 15 °C so what’s missing?  The short answer: an atmosphere which provides the natural greenhouse effect E =  T 4

8. ~4 x 10 26 W W = watts = power = energy/sec

9. Natural Greenhouse Effect

10. What Wavelength?  Sun ~6000 K, Earth ~288 K  Dominant Wavelength  Inversely related to temperature (Wien’s)  Hotter -> shorter wavelength  Sun @ 0.48  m (480 nm; visible)  Earth @ 10  m (infrared or IR)  Radiation emitted over a range of wavelengths  Sun ~6000 K, Earth ~288 K  Dominant Wavelength  Inversely related to temperature (Wien’s)  Hotter -> shorter wavelength  Sun @ 0.48  m (480 nm; visible)  Earth @ 10  m (infrared or IR)  Radiation emitted over a range of wavelengths

11. Note: shape of Earth’s spectrum. It’s modified by the atmosphere! Solar Peak Terrestrial Peak

12. What Happens To Insolation?  Reflection  Scattering  Absorption  Transmission  Reflection  Scattering  Absorption  Transmission

13. ReflectionReflection  Change in direction of a wave on encountering an interface  Atmosphere, clouds and surface  Measured by albedo  Change in direction of a wave on encountering an interface  Atmosphere, clouds and surface  Measured by albedo

14. Reflection (and albedo)  5-85%  = 35-75%

15. ScatteringScattering  Random redirection of light by the atmosphere  Wavelength and particle concentration dependence  Rayleigh (blue skies) and Mie (white clouds) are main processes  Random redirection of light by the atmosphere  Wavelength and particle concentration dependence  Rayleigh (blue skies) and Mie (white clouds) are main processes

16. ScatteringScattering

17. AbsorptionAbsorption  Energy taken up by object (photon is absorbed and destroyed)  Anything absorbed must be re-emitted to maintain equilibrium  At Earth temperatures, this converts shortwave into longwave when energy is re-emitted  Energy taken up by object (photon is absorbed and destroyed)  Anything absorbed must be re-emitted to maintain equilibrium  At Earth temperatures, this converts shortwave into longwave when energy is re-emitted

18. AbsorptionAbsorption

19. AbsorptionAbsorption  Atmosphere absorbs selectively (only some wavelengths)  Mostly transparent in visible range  Broad range of longwave absorbed by various greenhouse gases  Stratospheric O 2 & O 3 absorb UV  Atmosphere absorbs selectively (only some wavelengths)  Mostly transparent in visible range  Broad range of longwave absorbed by various greenhouse gases  Stratospheric O 2 & O 3 absorb UV

20. http://wxpaos09.colorado.edu/radiation/background.html IR or longwaveUV & Visible

21. http://www.atmos.washington.edu/~dennis/Energy_Flow.gif Shortwave 31% reflected directly 49% absorbed by surface 20% absorbed by atmosphere

22. http://www.atmos.washington.edu/~dennis/Energy_Flow.gif Longwave 390 W/m 2 is energy from a body at 15 °C

23. http://www.atmos.washington.edu/~dennis/Energy_Flow.gif Longwave

24. Longwave

25. Balance incoming

26. http://www.cdc.noaa.gov/ Outgoing Longwave Radiation

27. Additional complexity  Earth is a rough sphere  Slope, aspect  Latitude  Time/space varying albedo (reflectivity)  Vegetation, snow/ice, soils, moisture  Human land use change  Atmospheric composition/structure, clouds  Ocean, ice  Earth is a rough sphere  Slope, aspect  Latitude  Time/space varying albedo (reflectivity)  Vegetation, snow/ice, soils, moisture  Human land use change  Atmospheric composition/structure, clouds  Ocean, ice

28. Composition: Stable  Main components of dry atmosphere are pretty stable (~99%)  78% N 2, 21% O 2  Long-term (geologic) rise in oxygen  Changes in stable isotope ratios  Main components of dry atmosphere are pretty stable (~99%)  78% N 2, 21% O 2  Long-term (geologic) rise in oxygen  Changes in stable isotope ratios

29. Composition: Variable  Minor by volume (< 1%) but major by climate effect in many cases (GHGs)  Reactive (S, N, Cl cycles)  Non-reactive (CO 2, CFCs)  Water vapor (up to 4% by volume)  Particulates (aerosols)  Variation exists over many time and space scales  Minor by volume (< 1%) but major by climate effect in many cases (GHGs)  Reactive (S, N, Cl cycles)  Non-reactive (CO 2, CFCs)  Water vapor (up to 4% by volume)  Particulates (aerosols)  Variation exists over many time and space scales

30. Greenhouse gases  Certain naturally occurring trace gases change the atmosphere’s energy balance  Carbon dioxide (CO 2 ), Methane (CH 4 )  Water vapor and others…  Contribution to warming varies  By concentration  By “radiative efficiency”  By lifetime in the atmosphere  Certain naturally occurring trace gases change the atmosphere’s energy balance  Carbon dioxide (CO 2 ), Methane (CH 4 )  Water vapor and others…  Contribution to warming varies  By concentration  By “radiative efficiency”  By lifetime in the atmosphere

31. Leading Greenhouse Gases GasConcentration Carbon Dioxide (CO 2 ) 380 ppm Methane (CH 4 ) 1700 ppb Nitrous oxide (N 2 O) 500 ppb Ozone (O 3 ) 70 ppb Note: concentrations are approximate! Mexico ~one million people Mexico ~one million people India ~one billion people India ~one billion people

32. http://www.ipcc.ch/present/graphics/2001syr/large/02.01.jpg http://www.ipcc.ch -- Climate Change 2007: Summary for Policymakers

33. 33 Seasonal Cycle in NH Biota Anthropogenic Influence

34. Solar Base = 342 W m -2

35. Recent Change and Variability

36. http://www.ipcc.ch -- Climate Change 2007: The Physical Science Basis (Chapter 3) Recent Climate Variations: Surface Air Temperature

37. Ranked Global Temperatures http://www.ncdc.noaa.gov/sotc Tied

38. http://www.ipcc.ch -- Climate Change 2007: The Physical Science Basis (Chapter 3) Spatial Changes in Temperature

39. Muir Glacier, Alaska, August 13, 1941, photo by W.O. Field http://nsidc.org/data/glacier_photo/repeat_photography.html

40. Muir Glacier, Alaska, August 31, 2004, photo by B.F. Molnia, USGS http://nsidc.org/data/glacier_photo/repeat_photography.html

41. Grinnell Glacier 1938-2005 http://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850 1938 1981 Glacier National Park 2005

42. http://www.ipcc.ch -- Climate Change 2007: The Physical Science Basis (Chapter 3) Spatial Changes in Precipitation

43. http://www.ipcc.ch -- Climate Change 2007: The Physical Science Basis (Chapter 5) Recent Climate Variations: Sea Level

44. http://nsidc.org/sotc/sea_ice.html Arctic Sea Ice Trends

45. http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html Sept 2007 All-time Minimum

46. 500 Million Years of Change http://en.wikipedia.org/wiki/User:Dragons_flight/Images

47. 500 Million Years of Change http://en.wikipedia.org/wiki/User:Dragons_flight/Images

48. 500 Million Years of Change http://en.wikipedia.org/wiki/User:Dragons_flight/Images

49. Today is Different  Rates of change not seen in geologic record  World did not have nearly 7 billion people  Rates of change not seen in geologic record  World did not have nearly 7 billion people