Ecosystem nitrous oxide (N₂O) emissions respond to changes in climate and CO₂ concentration as well as anthropogenic nitrogen (N) enhancements. Here, we aimed to quantify the responses of natural ecosystem N₂O emissions to multiple environmental drivers using a process-based global vegetation model (DyN-LPJ).  We checked that modelled annual N₂O emissions from nonagricultural ecosystems could reproduce field measurements worldwide, and experimentally observed responses to step changes in environmental factors. We then simulated global N₂O emissions throughout the 20^th century and analysed the effects of environmental changes.  The model reproduced well the global pattern of N₂O emissions and the observed responses of N cycle components to changes in environmental factors. Simulated 20^th century global decadal-average soil emissions were c. 8.2–9.5 Tg N yr⁻¹ (or 8.3–10.3 Tg N yr⁻¹ with N deposition). Warming and N deposition contributed 0.85 ± 0.41 and 0.80 ± 0.14 Tg N yr⁻¹, respectively, to an overall upward trend. Rising CO2 also contributed, in part, through a positive interaction with warming.  The modelled temperature dependence of N₂O emission (c. 1 Tg N yr⁻¹ K⁻¹) implies a positive climate feedback which, over the lifetime of N₂O (114 yr), could become as important as the climate–carbon cycle feedback caused by soil CO₂ release. link to publication