Abstract
The human influence on vegetation causes changes in the surface reflective properties.
By using MODIS land cover and MODIS surface albedo products, an estimation of radiative forcing due to surface
albedo changes caused by vegetation changes is performed.
A potential natural vegetation data set is used to compute radiative forcing
estimates from pre agricultural times to present. A combination between MODIS blacksky and whitesky albedo and
diffuse and direct radiation at ground level makes it possible to improve the accuracy of the present surface albedo.
A new self-composed surface albedo data set is calculated for the purpose of
not overestimating the radiative forcing in snow covered cropland regions.
For that reason, a constraint on the pre agricultural data set is carried out by not allowing any surface albedo values
to be lower than 0.081. The best estimate shows a radiative forcing due to the surface albedo change
of -0.03 W/m2, which is weaker than what has been claimed earlier by previous studies. This is mainly because of a
more realistic value of cropland, the albedo constraint, and also the intrinsic power of the method consisting of combining
two MODIS products.