Land Use and Climate Land Use and Climate ChangeChange

Stephanie J HouserStephanie J Houser

Earth Climate SystemsEarth Climate Systems

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OutlineOutline Why be concerned with land Why be concerned with land

cover/land use changecover/land use change How do different land cover/land use How do different land cover/land use

changes affect climatechanges affect climate Climate model studiesClimate model studies

DOE-PCM A2 & B1 IPCC SRES (Feddema DOE-PCM A2 & B1 IPCC SRES (Feddema et al., 2005)et al., 2005)

CLM3 coupled model (Gibbard et al., CLM3 coupled model (Gibbard et al., 2005)2005)

Summary of findingsSummary of findings

Why?Why?

Changes in land Changes in land cover/use are major but cover/use are major but poorly recognized poorly recognized drivers of long-term drivers of long-term global climate patternsglobal climate patterns

May be as important as May be as important as changes in climate and changes in climate and weather associated with weather associated with greenhouse gasesgreenhouse gases

Changes often Changes often permanentpermanent

IPCC has yet to include IPCC has yet to include effect in assessmentseffect in assessments

Pielke 2005

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

Impacts on global climate divided into Impacts on global climate divided into two major categoriestwo major categories

Biogeochemical and BiogeophysicalBiogeochemical and Biogeophysical BiogeochemicalBiogeochemical

Chemical composition of the atmosphereChemical composition of the atmosphere BiogeophysicalBiogeophysical

Directly affect physical parameters that Directly affect physical parameters that determine absorption/distribution of energy determine absorption/distribution of energy at the earth’s sfcat the earth’s sfc

AlbedoAlbedo

How do these changes affect How do these changes affect climate?climate?

DeforestationDeforestation Warming due to Warming due to

decreased decreased evapotranspirationevapotranspiration

Modification of surface Modification of surface fluxes of heat and water fluxes of heat and water vaporvapor

ReforestationReforestation lowering of sfc albedo lowering of sfc albedo

leads to a net warmingleads to a net warming Increase sfc fluxes of Increase sfc fluxes of

water vaporwater vapor Cooling with vegetation Cooling with vegetation

at lower latitudes due to at lower latitudes due to evapotranspirationevapotranspiration

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Climate model studiesClimate model studies Fully coupled Department of Energy Fully coupled Department of Energy

Parallel Climate Model (DOE-PCM) Parallel Climate Model (DOE-PCM) Combined land-cover and atmospheric Combined land-cover and atmospheric

forcings for A2 and B1 IPCC SRES scenariosforcings for A2 and B1 IPCC SRES scenarios Land cover change – Integrated Model to Land cover change – Integrated Model to

Assess the Global Environment (IMAGE) Assess the Global Environment (IMAGE) IPCC SRES land-cover projections and DOE-IPCC SRES land-cover projections and DOE-PCM natural vegetation dataPCM natural vegetation data

For each SRES scenario, ran model fromFor each SRES scenario, ran model from 2000 to 2033 with present day land cover2000 to 2033 with present day land cover 2033 to 2066 with 2050 land cover2033 to 2066 with 2050 land cover 2066 to 2100 with 2100 land cover2066 to 2100 with 2100 land cover

(Feddema et al, 2005)(Feddema et al, 2005)

Feddema et al, 2005

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•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

Feddema et al, 2005

•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

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)

Feddema et al, 2005

Climate model studiesClimate model studies Not reproducing observed patterns of land Not reproducing observed patterns of land

cover change, nor realistically simulating cover change, nor realistically simulating possible future scenariospossible future scenarios

CAM3 (Community Atmosphere Model)CAM3 (Community Atmosphere Model) Coupled with the CLM land model and slab Coupled with the CLM land model and slab

ocean and thermo sea ice modelocean and thermo sea ice model Control runs with both current vegetation Control runs with both current vegetation

and bare soiland bare soil Two vegetated experiments, one with trees, and Two vegetated experiments, one with trees, and

one with grass/shrubs.one with grass/shrubs.

(Gibbard et al., 2005)(Gibbard et al., 2005)

a. 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

SummarySummary Changes in Land cover and Land use induce Changes in Land cover and Land use induce

changes in climate on regional and global scaleschanges in climate on regional and global scales Albedo-change and evapotranspiration effects Albedo-change and evapotranspiration effects

dominate cooling/warming of climatedominate cooling/warming of climate Overall warming due to reforestation (higher Overall warming due to reforestation (higher

latitudes)latitudes) Forestation causes cooling in Amazon, whereas Forestation causes cooling in Amazon, whereas

deforestation seems to cause warmingdeforestation seems to cause warming Evapotranspiration effects dominate at lower latsEvapotranspiration effects dominate at lower lats

Future research is needed to determine exact Future research is needed to determine exact nature of responses due to land use and land cover nature of responses due to land use and land cover change (Feddema et al., 2005)change (Feddema et al., 2005)

In order for IPCC to more accurately predict future In order for IPCC to more accurately predict future climates the effects of Land cover change and land climates the effects of Land cover change and land use change must be included in future assessmentsuse change must be included in future assessments

Questions?Questions?