Nitrous oxide (N2O), as a potent greenhouse gas, must be limited to prevent the global temperature increasing by >2 °C. Cropland is the largest source of anthropogenic N2O emissions; however, earlier estimates for emissions and their exceedances still remain uncertainties. Here, we used a spatially explicit model to estimate cropland N2O emission in 2014 by refined grid-level crop-specific EFs and considered the background emission. We also sought to determine where N2O emissions exceed the "boundary" through analysis of spatial data from representative concentration pathway (RCP) 2.6. The global cropland N2O emission was 2.92 ± 0.59 Tg N yr-1, which far exceeds the 0.82 Tg N yr-1 boundary, over 90 % of cropland areas exceeded the boundary. Western Europe, Southeastern China, Pakistan, and the Ganges Plain exceeded the boundary by >2 kg N ha-1 yr-1. The boundary exceedances showed a positive linear response with respect to total cropland emission and a quadratic response to GDP per capita at the country level. Our study highlights the necessity of accurate estimations of spatial variations in cropland N2O emissions and evaluation of exceedances, to facilitate the development of more effective mitigation measures in different regions.
Keywords: Boundary; Cropland; EFs; Exceedance; N(2)O emission.
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