Nitrous oxide (N2O) is the most important stratospheric ozone-depleting
agent based on current emissions and the third largest contributor to
increased net radiative forcing. Increases in atmospheric N2O have been
attributed primarily to enhanced soil N2O emissions. Critically,
contributions from soils in the Northern High Latitudes (NHL,
>50°N) remain poorly quantified despite their vulnerability
to permafrost thawing induced by climate change. An ensemble of six
terrestrial biosphere models suggests NHL soil N2O emissions doubled
since the preindustrial 1860s, increasing on average by 2.0±1.0 Gg N
yr-1 (p<0.01). This trend reversed after the 1980s because of
reduced nitrogen fertilizer application in non-permafrost regions and
increased plant growth due to CO2 fertilization suppressed emissions.
However, permafrost soil N2O emissions continued increasing attributable
to climate warming; the interaction of climate warming and increasing
CO2 concentrations on nitrogen and carbon cycling will determine future
trends in NHL soil N2O emissions.