N2O emissions from a fertilized humid grassland near Cork, Ireland were continuously measured during 2003 using an eddy covariance system. For most of the year emissions were close to zero and 60% of the emissions occurred in eight major events of 2-20 days' duration. Two hundred and seven kg ha(-1) of synthetic N and 130 kg ha(-1) organic N were applied over the year and the total measured annual N2O emission was 11.6 kg N ha(-1). The flux data were used to test the prediction of N2O emissions by the DNDC ( DeNitrification-DeComposition) model. The model predicted total emissions of 15.4 kg N ha(-1), 32 % more than the observed emissions. On this basis the model was further used to simulate ( a) background ( non-anthropogenic) N2O emissions and ( b) the effect on N2O emissions of future climate perturbations based on the Hadley Center model output of the IS92a scenario for Ireland. DNDC predicts 1.7 kg N ha(-1) year(-1) of background N2O emissions, accounting for 15% of the observed emissions. Climate shifts will increase total annual modeled N2O emissions from 15.4 kg N ha(-1) to 22.4 kg N ha(-1) if current levels of N applications are maintained, or to 21.2 kg N ha(-1) if synthetic N applications are reduced to 170 kg N ha(-1) to comply with recent EU water quality legislation. Thus the projected increase in N2O emissions due to climate change is far larger than the decrease expected from reduced fertilizer applications.