Nitrogen as a threat to the European greenhouse balance

Reactive nitrogen (N_r) is of fundamental importance in biological and chemical processes in the atmosphere-biosphere system, altering the Earth's climate balance in many ways. These include the direct and indirect emissions of nitrous oxide (N2O), atmospheric N_r deposition and tropospheric ozone formation (O3), both of which alter the biospheric CO2 sink, N_r supply effects on CH4 emissions, and the formation of secondary atmospheric aerosols resulting from the emissions of nitrogen oxides (NOx) and ammonia (NH3). Human production and release of N_r into the environment is thus expected to have been an important driver of European greenhouse balance. Until now, no assessment has been made of how much of an effect European N_r emissions are having on net warming or cooling