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Changes in Radiative Forcing

Changes in Radiative Forcing. Primary Source: IPCC WG-I Chapter 2 - Changes in Atmospheric Constituents and in Radiative Forcing. Key Findings. Extremely likely (> 95%) that humans have exerted a substantial warming influence on climate since 1750.

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Changes in Radiative Forcing

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  1. Changes in Radiative Forcing Primary Source: IPCC WG-I Chapter 2 - Changes in Atmospheric Constituents and in Radiative Forcing

  2. Key Findings Extremely likely (> 95%) that humans have exerted a substantial warming influence on climate since 1750. Likely (> 66%) that the human influence by radiative forcing is at least 5 times greater than solar influence since 1750. Exceptionally unlikely (< 1%) that solar + volcanic radiative forcing for 1950-2005 was comparable to anthropogenic radiative forcing.

  3. Major Types of Radiative Forcings Changes in … • Greenhouse Gases • Aerosols (particles) • Surface albedo • Contrails • Solar variability • Volcanic activity

  4. Radiative Forcing: Balanced State Radiative Balance Radiative-Dynamic Balance

  5. Radiative Forcing Change in net radiative energy flux at the tropopause with … (a) stratospheric temperatures readjusted to radiative equilibrium (b) surface and tropospheric temperatures and state held fixed at original values (Ramaswamy et al., 2001)

  6. Carbon Dioxide (CO2) Pre-industrial: ~ 280 ppm Sources: Fossil fuels Cement production Deforestation Biomass burning

  7. CO2 Emissions • O2 as CO2 : • Combustion • Plant respiration/photosynthesis 13C/12C: Atmosphere > Terrestrial Sources

  8. Methane (CH4) • Sources: • Biogenic: • Wetlands • Rice • Biomass burning • Ruminants • Fossil fuel mining and distribution • Living vegetation? NOAA Global Monitoring Division (GMD) Advanced Global Atmospheric Gases Experiments (AGAGE) Mt. Pinatubo? Warm 1998? Economic Incentives?

  9. Nitrous Oxide (N2O) • Sources: • Coastal areas: • continental shelves • estuaries • rivers • Land processes

  10. Halocarbons Small amounts, but effective absorbers of infrared radiation Factors: Industrial processes Partly regulated by Montreal Protocol

  11. Other Gases • Stratospheric Ozone • Tropospheric Ozone • Stratospheric Water Vapor

  12. Aerosol Effects

  13. Aerosol Types • Sulphate • Organic Carbon from Fossil Fuels • Black Carbon from Fossil Fuels • Biomass Burning • Nitrate • Mineral Dust

  14. Aerosol Distributions Optical Depth ~ Radiative “Thickness” White = measurement not possible Biomass Burning Mineral Dust Industrial Sea Salt

  15. Land Use Changes Albedo Differences Forest < Cropland Snow-covered forest < Snow-covered cropland

  16. Other Surface Effects • Black Carbon on Snow/Ice • Land-Use Changes on Surface Fluxes • Anthropogenic Water Vapor Release • Anthropogenic Energy Release • CO2 Influence on Plant Physiology

  17. Solar Heating: Change Variability due to 1. Changes in sunspots and faculae 2. Changes in solar diameter?

  18. Reconstructed Solar Heating

  19. Volcanic Aerosols

  20. Time Evolution of Forcing (Representative GCM)

  21. Net RF: 1750 to 2005

  22. END Changes in Radiative Forcing

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