Cooperative Institute for Research in Environmental Sciences

Science Rendezvous > 2009 Posters
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Investigations into the Climate Impacts of Land Cover Change in the Community Climate System Model

Peter J. Lawrence and Thomas Chase

The IPCC 4th Assessment Report suggests the net global impact of human land cover change is radiative cooling of -0.2 W/m2, principally through increased surface albedo under current day conditions. There have, however, been a wide range of conflicting investigations into the climate impacts of land cover change. To further understand the role of land cover change in the climate system we have performed a series of experiments with the Community Climate System Model (CCSM) with the land surface parameters of the Community Land Model (CLM) representing current day and potential vegetation conditions prior to human disturbance. The current day conditions have been derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery, while the potential vegetation has been generated from the mapping of Ramankutty and Foley (1999).

The impacts of the land cover change in CCSM were widespread with significant warming of up to 2.5 C regionally. In most cases, the warmer temperatures were associated with reduced evapotranspiration fluxes that were realized as increased sensible heat flux. In many areas the land cover change also was associated with reduced precipitation however the changes in precipitation were less robust than the changes in temperature. The largest impacts were found in Asia and Europe with smaller impacts in North America, South America, Africa and Australia, reflecting the scale of land cover change on each of these continents. The climate impacts also were predominantly driven by changes in hydrology with albedo playing a secondary role.

These finding have implications for land use management as well as our understanding of the climate system sensitivity to land cover change. There is the strong potential that we are substantially modifying regional climate as we continue to modify the land surface and the hydrological cycle through deforestation, urbanization, agricultural development, and through large scale irrigation schemes and hydrological engineering projects. This has implications for a number of carbon mitigation initiatives suggested for the next century, such as reforestation and biofuel production, as well.