Land Use and Climate Change

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Land Use and Climate Change

• Stephanie J Houser
• Earth Climate Systems

www.dcnr.state.pa.us
www.injuryupdate.com.au
www.gnb.ca
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Outline

• Why be concerned with land cover/land use change
• How do different land cover/land use changes
  affect climate
• Climate model studies
• DOE-PCM A2 B1 IPCC SRES (Feddema et al., 2005)
• CLM3 coupled model (Gibbard et al., 2005)
• Summary of findings

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Why?

• Changes in land cover/use are major but poorly
  recognized drivers of long-term global climate
  patterns
• May be as important as changes in climate and
  weather associated with greenhouse gases
• Changes often permanent
• IPCC has yet to include effect in assessments

Pielke 2005
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How do land cover/land use changes affect climate?

• Impacts on global climate divided into two major
  categories
• Biogeochemical and Biogeophysical
• Biogeochemical
• Chemical composition of the atmosphere
• Biogeophysical
• Directly affect physical parameters that
  determine absorption/distribution of energy at
  the earths sfc
• Albedo

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How do these changes affect climate?

• Deforestation
• Warming due to decreased evapotranspiration
• Modification of surface fluxes of heat and water
  vapor
• Reforestation
• lowering of sfc albedo leads to a net warming
• Increase sfc fluxes of water vapor
• Cooling with vegetation at lower latitudes due to
  evapotranspiration

www.greenpeace.org
www.auroville.org
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Climate model studies

• Fully coupled Department of Energy Parallel
  Climate Model (DOE-PCM)
• Combined land-cover and atmospheric forcings for
  A2 and B1 IPCC SRES scenarios
• Land cover change Integrated Model to Assess
  the Global Environment (IMAGE) IPCC SRES
  land-cover projections and DOE-PCM natural
  vegetation data
• For each SRES scenario, ran model from
• 2000 to 2033 with present day land cover
• 2033 to 2066 with 2050 land cover
• 2066 to 2100 with 2100 land cover
• (Feddema et al, 2005)

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Feddema et al, 2005
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fd

• Temperature change
• All forcing scenario minus atmospheric forcing
  with constant land cover
• Most significant regional climate effects are
  associated with changes in mid-latitude and
  tropical regions

Feddema et al, 2005

• Tropical regions with same land cover forcings
  have different responses
• Amazon warming due to change from broadleaf
  forest to agriculture
• Net radiation changes in atm forcing scenarios
  offset by increases in latent heat fluxes when
  forests are present
• Land-cover and atm forcing simulations, reduced
  latent heat flux, increased incident radiation
• Indonesia - lack of response attributed to Asian
  Monsoon circulation which override feebacks from
  local land-cover change

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Feddema et al, 2005

• Diurnal Temperature Range
• More significant impact
• Decreases significantly in southern Asia
• (A2) Midlatitide regions experience decrease in
  DTR
• In the Amazon, significant increase in daily
  minimum temperatures (nighttime)

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Climate model studies

• Not reproducing observed patterns of land cover
  change, nor realistically simulating possible
  future scenarios
• CAM3 (Community Atmosphere Model)
• Coupled with the CLM land model and slab ocean
  and thermo sea ice model
• Control runs with both current vegetation and
  bare soil
• Two vegetated experiments, one with trees, and
  one with grass/shrubs.
• (Gibbard et al., 2005)

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• Temperature difference between the tree
  simulation and bare soil simulation
• Heating effects of forest in upper latitudes
• Albedo-change dominates over evapotranspiration
• b. Vegetation from 20-50N replaced by forest,
  rest of vegetation current
• - Direct effect of trees is warming (more
  than with bare ground)
• c. Albedo change (bare vs. tree)
• - Snow-albedo feedback effect responsible
  for 25 of change in sfc albedo between bare and
  tree simulations
• - Max albedo change in North where snowfall
  has decreased due to increased temperatures

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Summary

• Changes in Land cover and Land use induce changes
  in climate on regional and global scales
• Albedo-change and evapotranspiration effects
  dominate cooling/warming of climate
• Overall warming due to reforestation (higher
  latitudes)
• Forestation causes cooling in Amazon, whereas
  deforestation seems to cause warming
• Evapotranspiration effects dominate at lower lats
• Future research is needed to determine exact
  nature of responses due to land use and land
  cover change (Feddema et al., 2005)
• In order for IPCC to more accurately predict
  future climates the effects of Land cover change
  and land use change must be included in future
  assessments

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Questions?