changes in radiative forcing

(Mt/Ag/EnSc/EnSt 404/504 - Global Change)(Mt/Ag/EnSc/EnSt 404/504 - Global Change) Radiative Forcing (from IPCC WG-I, Chapter 2)Radiative Forcing (from IPCC WG-I, Chapter 2)

Changes in Radiative ForcingChanges in Radiative Forcing

Primary Source: Primary Source:

IPCC WG-I Chapter 2 - IPCC WG-I Chapter 2 - Changes in Atmospheric Constituents and in Radiative ForcingChanges in Atmospheric Constituents and in Radiative Forcing


Key FindingsKey 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 (< 1%) that solar + volcanic radiative forcing for 1950-2005 was comparable to anthropogenic radiative forcing.


Major Types of Radiative ForcingsMajor Types of Radiative Forcings

Changes in …Changes in …• Greenhouse GasesGreenhouse Gases• Aerosols (particles)Aerosols (particles)• Surface albedoSurface albedo• ContrailsContrails• Solar variabilitySolar variability• Volcanic activityVolcanic activity


Radiative Forcing: Balanced StateRadiative Forcing: Balanced State

Radiative BalanceRadiative Balance

Radiative-Dynamic BalanceRadiative-Dynamic Balance


Radiative ForcingRadiative Forcing

Change in net radiative energy flux at the tropopause with …Change in net radiative energy flux at the tropopause with …(a) stratospheric temperatures readjusted to radiative equilibrium(a) stratospheric temperatures readjusted to radiative equilibrium(b) surface and tropospheric temperatures and state held fixed at (b) surface and tropospheric temperatures and state held fixed at

original valuesoriginal values(Ramaswamy et al., 2001)(Ramaswamy et al., 2001)


Carbon Dioxide Carbon Dioxide (CO(CO22))

Pre-industrial: ~ 280 ppmPre-industrial: ~ 280 ppm

Sources:Sources:

1.1. Fossil fuelsFossil fuels

2.2. Cement productionCement production

3.3. DeforestationDeforestation

4.4. Biomass burningBiomass burning


COCO22 Emissions Emissions

1313C/C/1212C: C: Atmosphere > Terrestrial SourcesAtmosphere > Terrestrial Sources

OO22 as CO as CO22 : :

- CombustionCombustion

- Plant respiration/photosynthesisPlant respiration/photosynthesis


Methane (CHMethane (CH44))

NOAA Global Monitoring Division (GMD)

Advanced Global Atmospheric Gases Experiments (AGAGE)

Sources:Sources:

1.1. Biogenic:Biogenic:

- WetlandsWetlands

- RiceRice

- Biomass burningBiomass burning

- RuminantsRuminants

2.2. Fossil fuel mining Fossil fuel mining and distributionand distribution

3.3. Living vegetation?Living vegetation?

Mt. Pinatubo?

Economic Incentives?

Warm 1998?


Nitrous Oxide (NNitrous Oxide (N22O)O)

Sources:Sources:

1.1. Coastal areas:Coastal areas:

- continental continental shelvesshelves

- estuariesestuaries

- riversrivers

2.2. Land processesLand processes


HalocarbonsHalocarbons

Small amounts, but Small amounts, but effective absorbers of effective absorbers of infrared radiationinfrared radiation

Factors:Factors:

1.1. Industrial Industrial processesprocesses

2.2. Partly regulated Partly regulated by Montreal by Montreal ProtocolProtocol


Other GasesOther Gases

• Stratospheric OzoneStratospheric Ozone

• Tropospheric OzoneTropospheric Ozone

• Stratospheric Water VaporStratospheric Water Vapor


Aerosol EffectsAerosol Effects


Aerosol TypesAerosol Types

• SulphateSulphate

• Organic Carbon from Fossil FuelsOrganic Carbon from Fossil Fuels

• Black Carbon from Fossil FuelsBlack Carbon from Fossil Fuels

• Biomass BurningBiomass Burning

• NitrateNitrate

• Mineral DustMineral Dust


Aerosol Aerosol DistributionsDistributions

Biomass BurningBiomass Burning

Optical Depth ~ Radiative “Thickness”Optical Depth ~ Radiative “Thickness”

White = measurement not possibleWhite = measurement not possible

Mineral DustMineral Dust

IndustrialIndustrial

Sea SaltSea Salt


Land Use ChangesLand Use Changes

Albedo DifferencesAlbedo DifferencesForest < CroplandForest < Cropland

Snow-covered forest < Snow-covered forest < Snow-covered croplandSnow-covered cropland


Other Surface EffectsOther Surface Effects

• Black Carbon on Snow/IceBlack Carbon on Snow/Ice

• Land-Use Changes on Surface FluxesLand-Use Changes on Surface Fluxes

• Anthropogenic Water Vapor ReleaseAnthropogenic Water Vapor Release

• Anthropogenic Energy ReleaseAnthropogenic Energy Release

• COCO22 Influence on Plant Physiology Influence on Plant Physiology


Solar Heating: ChangeSolar Heating: Change

Variability due to Variability due to

1. Changes in sunspots and faculae1. Changes in sunspots and faculae

2. Changes in solar diameter?2. Changes in solar diameter?


Reconstructed Solar HeatingReconstructed Solar Heating


Volcanic AerosolsVolcanic Aerosols


Time Evolution of Time Evolution of Forcing Forcing

(Representative GCM)(Representative GCM)


Net RF: Net RF: 1750 to 20051750 to 2005


ENDEND

Changes in Radiative ForcingChanges in Radiative Forcing

changes in radiative forcing

Documents