Contribution of the anthropogenic reactive nitrogen (Nr) and other terrestrial ecosystem changes to present-day radiative forcing. Radiative forcing of (a) CO2 and (b) N2O in the year 2005. Distinguished are the marginal biogeochemical effects of changes in land-cover (yellow), CO2 fertilization (blue), climate change (red), and Nr additions (green; from bottom to top: nitrogen deposition, nitrogen fertilizer, riverine, manure) on the atmospheric concentrations of CO2 and N2O. The black bar denotes the total terrestrial forcing and the grey bar the observed radiative forcing. Error bars denote uncertainty (1) in radiative forcing estimates.