COS 21-3 - Regionally-differentiated estimates of cropland N2O emissions reduce uncertainty in global calculations

Tuesday, August 9, 2011: 8:40 AM
6A, Austin Convention Center
Aaron B. Berdanier, University Program in Ecology, Duke University, Durham, NC and Richard T. Conant, Institute for Sustainable Resources, Queensland University of Technology, Brisbane, Australia

Nitrogen (N) additions to agricultural soils are the largest source of anthropogenic nitrous oxide (N2O) emissions and are an important contributor to global greenhouse gas radiative forcing. Progress in understanding controls on N2O fluxes from soils is demonstrated in increasingly sophisticated emissions estimates with improved spatial and source resolution. These methods build upon ongoing field, laboratory, and modeling advances that are restricted to just a handful of countries. Thus burgeoning new knowledge is of limited utility for improving N2O emission estimates for the rest of the world where prospects for near-term advances are constrained by the limited breadth of observations. Here we use Bayesian inversion to leverage information from recent national-level N2O emission inventories and data on background emissions from a breadth of field sites to estimate parameters for calculating direct cropland emissions.


The Bayesian inversion produced regional emission parameter estimates with greater confidence than prior default factors, resulting in a 75% reduction in uncertainty for calculations of regional and global cropland N2O emissions. Our estimates of the proportion of N inputs lost as N2O vary by nearly a factor of three between regions and depart substantially from existing default emission factors, yet regional emission calculations based on these factors are consistent with global, regional, and local observations. Improved regional emission factors will enhance national greenhouse gas inventories in information-poor countries and direct efforts to reduce agricultural N2O emissions.

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