Natural and Anthropogenic Controls over Global Terrestrial N2O Emission Growth at a Century-Long Time Scale

The Atmospheric concentration of nitrous oxide (N₂O) has increased by 20% relative to pre-industrial level. It has attracted growing attention since N₂O has long life time and radiative forcing 265 times higher than CO₂ at 100-year time horizon. Global N₂O emission from terrestrial ecosystem is among the most important contributors to the increase of atmospheric N₂O. However, compared to CO₂- and CH₄-related research, less intensive studies have been performed in assessing the spatiotemporal patterns of terrestrial N₂O emission and attributing its changes to both natural and anthropogenic disturbances across the globe. Here we integrated gridded time-series data of climate variability, atmospheric CO₂ concentration, nitrogen deposition, land use and land cover changes, and agricultural land management practices (i.e., synthetic nitrogen fertilizer use, manure application, and irrigation etc.) to a process-based land ecosystem model, DLEM, for answering the above questions.

During 1900-2010, the inter-annual variation and long-term trend of terrestrial N₂O emission driven by individual and combined environmental changes have been examined. Through this, we distinguished and quantified the relative contributions of changes in climate, atmospheric composition, and human activities to N₂O emission growth at biome-, latitudinal, continental and global scales. The impacts of climate variability, and increasing nitrogen input, particularly nitrogen fertilizer use along with enhanced food production, have been paid special attention. Hot spots and hot time periods of global N₂O emission are identified in this study. It provides clue for scientific community and policy makers to develop potential management strategies for mitigating atmospheric N₂O increase and climate warming.