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Climate Change

Climate Change. Advanced Placement Conference Augusta, ME October 30, 2009. Overview. Solar Energy Budget Evidence of Past Climate Assessment of Current Climate Climate Projections Effects of Climate Change Current U.S. Legislative Action Making Climate Change Personal.

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Climate Change

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  1. Climate Change Advanced Placement Conference Augusta, ME October 30, 2009

  2. Overview • Solar Energy Budget • Evidence of Past Climate • Assessment of Current Climate • Climate Projections • Effects of Climate Change • Current U.S. Legislative Action • Making Climate Change Personal

  3. Disparity in the Budget Incoming Shortwave Outgoing Long wave

  4. Disparity in location

  5. Solar Irradiance • Total solar irradiance is maximum power (watts or j/s) that the sun can deliver to a surface perpendicular to the path of light • Areas near the equator at noon come close to this total • Both latitude and time of day affect the irradiance received by a particular area • On the equinox: • Tropics ~ ~ 90% • Mid-Latitudes ~ 70% • Arctic and Antarctic ~ 40% • Overall ~ 25%

  6. Disparity in Time of Day

  7. Irradiance and Time of Year

  8. Albedo and Net Energy Reflected Solar Energy Net Energy Gain/Loss

  9. The Climate Engine • The net heating imbalance drives powerful atmospheric and oceanic circulations • This driving force is called an “engine” because it converts energy into motion • The effects of these imbalances and circulations are what causes the climate of a particular location • Evaporation, convection precipitation, winds, and oceanic currents are all parts of this climate engine

  10. Data Collection • Exact values for earth energy flows are unknown and a subject of intense research • Different Estimates exist and all estimates have some uncertainty • Estimates come from: • Satellite observations • Ground and sea-based observations • Numerical climate models

  11. The Earth’s Energy Budget • The climate engine moves heat vertically through the atmosphere and into space as well as along the surface • The sum of the incoming energy and outgoing energy flow determines the temperature of the earth • Ei = Eo temperature is stable • Ei > Eo earth’s temperature increases • Ei < Eo earth’s temperature decreases

  12. Energy Budget(incoming)

  13. Outgoing Energy • Absorbed incoming solar energy (shortwave Ei) increases the temperature of the molecules that absorb the energy • These molecules in turn, radiate energy as heat (long wave Eo) • The amount of energy radiated is proportional to T4 • If temperature doubles: • E = T4 = 24 = 16 times amount of energy

  14. Outgoing = ƒ (Incoming) Long wave Radiation Shortwave radiation

  15. The Reshuffling of Heat Loss • The earth’s surface and atmosphere absorb 71% of incoming solar radiation • The atmosphere absorbs 23%, but radiates 59% of the solar radiation • The surface absorbs 48%, but radiates only 12% of the solar radiation • How does this reshuffling of heat energy happen?

  16. Surface Energy Balance

  17. Surface Processes • Evaporation / Condensation / Freezing • About 25% of energy loss / gain • Latent heat • Principle driver of atmospheric heat engine • Conduction / Convection • The fallacy of “Hot Air Rises” • Radiation • Infrared (λ = ~12.5 µm, ƒ = ~24 THz)

  18. Adding Surface Heat to the Atmosphere

  19. The Problematic 6% • ~ 59% of the earth’s energy is radiated from the atmosphere • 23% comes directly from the sun • 25% comes from evaporation / condensation processes • 5% comes from conduction / convection • Where does the other 6% come from???

  20. Atmosphere Energy Balance

  21. Greenhouse Gases • Certain molecules within the atmosphere absorb some of the radiation emitted by the surface. This raises their temperature • Asymmetry – mass – bond strength • Once the energy is absorbed, it is re-radiated in all directions, some of it returns to the surface • This return of heat energy to the surface, increases its temperature by ~ 15oC

  22. Total Energy Budget

  23. Runaway Greenhouse Effect? • Radiation energy increases as T4 • As the surface warms up, so does the atmosphere which increases the rate of transfer from bottom of atmosphere to the top where it eventually escapes • When top of atmosphere radiation equals incoming solar radiation (79%), the earth’s energy budget is balanced and the temperature remains stable • What could de-stabilize this balance?

  24. Climate Forcings Volcano Forcings Anthropogenic Forcings

  25. The Water-Vapor Window • Water vapor is strong absorber of infrared radiation, but not at all frequencies • Infrared radiation at particular frequencies is “invisible” to water vapor. • These are the water vapor windows and radiation emitted at these frequencies escapes freely into space (Most important is the 10µ m window) • Unless a different atmospheric molecule can absorb these radiations and partially “close” the water-vapor window

  26. Closing the Window

  27. Other De-Stabilizing Factors • Sun output changes – sunspots • Orbital / tilt changes of the earth • Continental drift • Vegetative changes

  28. Modifying Factors • Heat capacity of the oceans • 1.3 x 109 km3 • Temperature – Radiation balance (T4) • Effect of clouds????

  29. Current Imbalance • Difficult to measure but appears to be about 0.8 Watt/m2 (average = 240 Watt/m2 • Global average surface temperature (GAST) has risen between 0.6 – 0.9o C in the last century • It will likely rise at least another 0.6o C, due to the current imbalance • What if the imbalance gets larger????

  30. Past Climate Reconstruction • Instrumental Data • Measurements • Historical records • Proxy Data • Use of O16 – O18 ratio • Ice cores • Tree Rings (high elevations) • Lake and ocean sediments (pollen, plankton, and dust) • Coral growth bands

  31. Oxygen Isotopes

  32. O-18 % in Precipitation

  33. O-18: O-16 Ratio

  34. General Predictions • Change in climate temperature – some cooler, some warmer • Increased frequency of extreme weather events • Vegetation shifts • e.g. Great Plains become forested • Animal shifts follow • Human health negatively affected

  35. Plant Response - Favorable • C-3 Plants (Wheat, Rice, Soybean) respond readily to increased CO2 concentrations (lab results) • C-4 plants (Corn, Sorghum, Sugarcane, Millet) do not respond to increase in CO2 concentrations (lab results) • Stomata open less frequently thus conserving water loss

  36. Plant Response – Unfavorable or ? • Higher temperatures lead to photorespiration decreasing photosynthetic yield • Changes in rainfall (amounts and patterns) affect natural flora and traditional agricultural crops • Greater frequency of extreme weather events will affect plants, but the extent is unknown

  37. Crop Yield: Four Staple Crops

  38. Crop Yield: Four Staple Crops

  39. Agriculture • Demand for water is expected to rise • Water resources are already dwindling • Increase in soil temperature • Drier soils – less root development • Affect on nitrogen fixation • Affect on soil erosion • More fertilizers needed especially in newly marginal areas • Mid-latitudes • High Latitudes • More Energy Used by agriculture

  40. Human Health • Probably the greatest impact of Climate Change • Food and Water shortage • Estimate 17% drop in food with 1o C temperature change • Poor sanitation • Flooding overwhelming sewage treatment • Greater pathogen spread • Tropical diseases: malaria and dengue fever • US 1300 cases, 8 deaths (2002) • Worldwide 350 000 000 cases: one million deaths that’s 2 deaths per minute

  41. Discrepancies: Winners and Losers

  42. Discrepancies: Developing Nations • Poor will be hardest hit • Most dependent on natural resources • Less Availability of medical care • Less capable of mitigating affects • Least responsible for climate change

  43. Abrupt Change • Paleocene – Eocene thermal Maximum (PETM) • 6o in 20,000 years • 2 short 1000 yr pulses - clathrates • Non-Linear CO2 – Temperature relationship • Positive Feedback Loops • Negative Feedback Loops • Something Else?????

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