Increasing sensitivity of terrestrial nitrous oxide emissions to precipitation variations

Abstract

Abstract Nitrous oxide (N2O), a major greenhouse gas and ozone-depleting agent, is generated over land mostly from two key biochemical processes—nitrification and denitrification. Nitrifying and denitrifying N2O production occurs preferably under alternative oxic and anoxic conditions, which are closely linked with variations in water filled soil pores, and thus indirectly with precipitation. We show here that the interannual anomalies in the annual growth rate of the global land N2O emissions are significantly (P < 0.001) correlated with precipitation anomalies, with an overall sensitivity ( α PRE , changes of land N2O emission variations per precipitation anomalies) of 2.50 ± 0.98 Tg N2O–N per 100 mm of precipitation across the global land (1998–2016). The sensitivity ( α PRE ) and precipitation-driven N2O anomalies increased during 1998–2016, partly due to increased nitrogen inputs to agricultural lands and enhanced precipitation anomalies. Spatially, we find that the α PRE increases with aridity. We predict a larger α PRE under future climate conditions (with radiative forcing levels of 4.5, 7.0 and 8.5 Wm−2) by the year 2100 if nitrogen fertilization follows the present practice.