The Impact of Albedo Change on Carbon Sequestration Strategies

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The Impact of Albedo Change on Carbon
Sequestration Strategies

• Maithilee Kunda
• Gregg Marland
• Lorenza Canella
• Bernhard Schlamadinger
• Neil Bird

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What is albedo?

• albedo reflected radiation incident
  radiation

albedo 0.5
albedo 1.0
albedo 0.0
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(No Transcript)
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Land albedo is a function of...

• Vegetation
• Snow cover
• Soil color
• Elevation and slope
• Time of day
• Time of year
• Latitude
• ... ?

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Albedos of Different Land Covers
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Why do we care?

• land cover change causes albedo change, which
  effects the surface energy balance
• in particular, field to forest causes a BIG
  change, especially in snowy conditions

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Global effects of albedo change

• Bonan, Pollard, Thompson. (1992) Effects of
  boreal forest vegetation on global climate.
  Nature 359.
• boreal deforestation has a cooling effect
• cooling perpetuated by thermal reservoir of
  oceans and by ice-albedo positive feedback
• Betts (2000). Offset of the potential carbon
  sink from boreal forestation by decreases in
  surface albedo. Nature 408.
• albedo warming effect is significant in magnitude
  compared to cooling effect of carbon
  sequestration
• warming may offset cooling in boreal regions

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Studying albedo change locally

• 1 hectare 10,000 m2
• reforestation of fields
• deciduous or coniferous
• varying latitudes
• more snow cover at higher latitudesmore albedo
  effect
• less incoming radiation at higher latitudesless
  albedo effect

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A simple beginning

• Albedo as a function of
• land cover
• month
• snow cover
• Simple radiation model using NREL data of average
  monthly solar insolation
• no variable for cloud cover
• no hydrologic cycle or latent heat fluxes

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Example Caribou, Maine
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Example Caribou, Maine
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The basic logic

• A change in local carbon stocks
• Creates a local change in surface albedo
• Creates a local change in the mean annual
  radiative flux
• Causes a global mean annual radiative forcing
• Which can be equated with a change in atmospheric
  carbon burden
• Which we compare to the initial change in local
  carbon stocks

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Albedo change to carbon change

• Mean annual radiative forcing F
• Atmospheric CO2 equivalence
• F 5.35 ln (1 ?C / C)
• Terrestrial carbon equivalence T
• T (Mc / Ma) m ?C
• adapted from Betts, 2000

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GORCAM
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The time-scale issue

• Change in land surface generates a permanent
  change in surface albedo
• A pulse of CO2 to (or from) atmosphere will decay
  with time as atmosphere equilibrates with the
  rest of the global carbon cycle
• Therefore, we treat all flows of carbon as annual
  pulses and let them decay with time.
• CO2(t) CO2(initial) a0 ?aie-t/zi for i
  1 to 4 from Maier-Reimer and Hasselman, 1987

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CO2 decay function
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Preliminary resultscarbon stock changes -
Worcester, MA
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Preliminary resultscarbon stock changes
Caribou, ME
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Preliminary resultsradiative impacts
Worcester, MA
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Preliminary resultsradiative impacts Caribou,
ME
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Further albedo investigations

• better albedo representation
• vegetation type, growth rates
• snow cover, climate-vegetation feedbacks
• GORCAM model
• alternate scenarios involving forest products and
  bioenergy production
• ways to think about clouds and latent heat
• might temper albedo effect

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Conclusions

• Complex system
• This study only estimates relative magnitudes of
  albedo effect and sequestration effect, which
  seem to be comparable
• Carbon balance is not the whole story
• Surface energy balances appear to be important
  and need systematic consideration

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Acknowledgements

• DOE Global Change Education Program (GCEP)
• DOE Office of Science, Biological and
  Environmental Research (BER)