radiative forcing
DESCRIPTION
Radiative Forcing. The balance between incoming solar radiation and heat radiation leaving the atmosphere. Key Findings. Extremely likely (> 95%) that humans have exerted a substantial warming influence on climate since 1750. - PowerPoint PPT PresentationTRANSCRIPT
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Radiative Forcing
The balance between incoming solar radiation and
heat radiation leaving the atmosphere.
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Key Findings
1.Extremely likely (> 95%) that humans have exerted a substantial warming influence on climate since 1750.
2.Likely (> 66%) that the human influence by radiative forcing is at least 5 times greater than solar influence since 1750.
3.Exceptionally unlikely (> 99%) that solar + volcanic radiative forcing for 1950-2005 was comparable to anthropogenic radiative forcing.
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Major Types of Radiative Forcings
Changes in …
Greenhouse Gases
Aerosols (particles)
Surface albedo
Contrails
Solar variability
Volcanic activity
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Our Variable Star
Changes of ~ 0.2% (= 2.7 W m-2) reflect 11-year sunspot cycle
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Radiative Forcing: Balanced State
Radiative Balance
Radiative-Dynamic Balance
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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
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Carbon Dioxide (CO2)Pre-
industrial: ~ 280 ppm
Sources:1. Fossil fuels2. Cement
production3. Deforestation4. Biomass
burning
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CO2 Emissions
13C/12C: Atmosphere >
Terrestrial Sources
O2 as CO2 : Combustion Plant respiration/photosy
nthesis
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Methane (CH4)
NOAA Global Monitoring Division (GMD)
Advanced Global Atmospheric Gases Experiments (AGAGE)
Sources:Biogenic:WetlandsRiceBiomass burningRuminantsFossil fuel mining & distribution Living vegetation?
Mt. Pinatubo?
Economic Incentives?
Warm 1998?
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Nitrous Oxide (N2O)
Sources:Coastal areas:continental shelves estuaries riversLand processes
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Halocarbons
Small amounts, but effective absorbers of infrared radiationFactors:Industrial processesPartly regulated by Montreal Protocol
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Other Gases
Stratospheric Ozone Tropospheric Ozone Stratospheric Water Vapor
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Aerosol Effects
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Aerosol Types
Sulphate Organic Carbon from Fossil Fuels Black Carbon from Fossil Fuels Biomass Burning Nitrate Mineral Dust
Aerosol Distributions
Biomass Burning
Optical Depth: Radiative Thickness”
Mineral Dust
Industrial
Sea Salt
White: measurement not possible
Land Use Changes
Albedo DifferencesForest < CroplandSnow-covered forest < Snow-covered cropland
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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
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Solar Heating: Change
Variability due to 1. Changes in sunspots and
faculae2. Changes in solar diameter?
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Reconstructed Solar Heating
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Volcanic Aerosols
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Time Evolution of Forcing (Representative GCM)
Net RF: 1750 to 2005
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Changes in Radiative Forcing