|JIAO, TONG - Clark University
|WILLIAMS, CHRISTOPHER - Clark University
|GHIMIRE, BARDEN - Clark University
|MASEK, JEFFREY - Goddard Space Flight Center
|SCHAAF, CRYSTAL - University Of Massachusetts
Submitted to: Journal of Climate Change
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/31/2017
Publication Date: 4/21/2017
Citation: Jiao, T., Williams, C., Ghimire, B., Masek, J., Gao, F.N., Schaaf, C. 2017. Global climate forcing from albedo change caused by large-scale deforestation and reforestation: quantification and attribution of geographic variation. Journal of Climate Change. doi:10.1007/s10584-017-1962-8.
Interpretive Summary: Deforestation and conversion to cropland is one of the most widespread land cover changes and typically yields the largest climate effects in part due to the change of albedo-induced radiative forcing. Associated warming and cooling varies widely across the globe, but resulting geographic variation is not well understood. This paper provides an observation-based approach to quantify local and global radiative forcings from large-scale deforestation and reforestation using albedo look-up maps and a historical land use data set. Snow-cover fraction is identified as the primary factor causing wintertime spatial variation of radiative forcing for a given type of forest gain or loss, while the change in snow-free albedo is of key importance during summer. Understanding the impacts of land cover and land use change is critical for the USDA in order to develop mitigation strategies for sustainable agricultural production and forest management.
Technical Abstract: Large-scale deforestation and reforestation have contributed substantially to historical and contemporary global climate change in part through albedo-induced radiative forcing, with meaningful implications for forest management aiming to mitigate climate change. Associated warming or cooling varies widely across the globe due to a range of factors including forest type, snow cover, and insolation, but resulting geographic variation remains poorly described, and has been largely based on model assessments. This study provides an observation-based approach to quantify local and global radiative forcings from large-scale deforestation and reforestation, and further examines mechanisms that result in the spatial heterogeneity of radiative forcing. We incorporate a new spatially and temporally explicit, land cover specific albedo product derived from Moderate Resolution Imaging Spectroradiometer with a historical land use data set (Land Use Harmonization product). Spatial variation in radiative forcing was attributed to four mechanisms, including the change in snow-covered albedo, change in snow-free albedo, snow-cover fraction and incoming solar radiation. We find an albedo-only radiative forcing (RF) of -0.819 W m-2 if year 2000 forests were completely deforested and converted to croplands. Albedo RF from global reforestation of present-day croplands that were previously forested is estimated as 0.265 W m-2. Snow-cover fraction is identified as the primary factor in determining the spatial variation of radiative forcing in winter, while the magnitude of the change in snow-free albedo is the primary factor determining variations in summertime RF. Findings reinforce the notion that, for conifers at the snowier high latitudes, albedo RF diminishes the warming from forest loss and the cooling from forest gain more so than for other forest types, latitudes, and climate settings.