Land cover and land use change may have an
impact on the surface albedo, evapotranspiration, sources and sinks
of heat - trapping
gases (
greenhouse gases), or other properties
of the climate system and may thus have a
radiative forcing and / or other
impacts on climate, locally or globally.
Tyndall's main interest was with water vapour and its
impact on radiation, but he also dealt with the
radiative forcing
of other
greenhouse gases including carbon dioxide.
In terms
of greenhouse agents, the main conclusions from the WGI FAR Policymakers Summary are still valid today: (1) «emissions resulting from human activities are substantially increasing the atmospheric concentrations
of the
greenhouse gases: CO2, CH4, CFCs, N2O»; (2) «some
gases are potentially more effective (at
greenhouse warming)»; (3) feedbacks between the carbon cycle, ecosystems and atmospheric
greenhouse gases in a warmer world will affect CO2 abundances; and (4) GWPs provide a metric for comparing the climatic
impact of different
greenhouse gases, one that integrates both the
radiative influence and biogeochemical cycles.