Data-driven estimates of global nitrous oxide emissions from croplands

Qihui Wang; Feng Zhou; Ziyin Shang; Philippe Ciais; Wilfried Winiwarter; Robert B Jackson; Francesco N Tubiello; Greet Janssens-Maenhout; Hanqin Tian; Xiaoqing Cui; Josep G Canadell; Shilong Piao; Shu Tao

doi:10.1093/nsr/nwz087

Data-driven estimates of global nitrous oxide emissions from croplands

Natl Sci Rev. 2020 Feb;7(2):441-452. doi: 10.1093/nsr/nwz087. Epub 2019 Jul 11.

Authors

Qihui Wang¹, Feng Zhou¹, Ziyin Shang¹, Philippe Ciais^{1

2}, Wilfried Winiwarter^{3

4}, Robert B Jackson⁵, Francesco N Tubiello⁶, Greet Janssens-Maenhout⁷, Hanqin Tian⁸, Xiaoqing Cui¹, Josep G Canadell⁹, Shilong Piao¹, Shu Tao¹

Affiliations

¹ Sino-France Institute of Earth Systems Science, Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
² Laboratoire des Sciences du Climat et de l'Environnement, LSCE, CEA CNRS UVSQ, Gif sur Yvette 91191, France.
³ International Institute for Applied Systems Analysis (IIASA), Laxenburg A-2361, Austria.
⁴ The Institute of Environmental Engineering, University of Zielona Góra, Zielona Góra 65-417, Poland.
⁵ Department of Earth System Science, Stanford University, Stanford 94305, USA.
⁶ Statistics Division, Food and Agricultural Organization of the United Nations, Via Terme di Caracalla, Rome 00153, Italy.
⁷ European Commission, Joint Research Centre, Ispra 21027, Italy.
⁸ International Center for Climate and Global Change Research, School of Forestry and Wildlife Sciences, Auburn University, Auburn, Alabama 36849, USA.
⁹ Global Carbon Project, CSIRO Oceans and Atmosphere, Canberra ACT 2601, Australia.

Abstract

Croplands are the single largest anthropogenic source of nitrous oxide (N₂O) globally, yet their estimates remain difficult to verify when using Tier 1 and 3 methods of the Intergovernmental Panel on Climate Change (IPCC). Here, we re-evaluate global cropland-N₂O emissions in 1961-2014, using N-rate-dependent emission factors (EFs) upscaled from 1206 field observations in 180 global distributed sites and high-resolution N inputs disaggregated from sub-national surveys covering 15593 administrative units. Our results confirm IPCC Tier 1 default EFs for upland crops in 1990-2014, but give a ∼15% lower EF in 1961-1989 and a ∼67% larger EF for paddy rice over the full period. Associated emissions (0.82 ± 0.34 Tg N yr^-1) are probably one-quarter lower than IPCC Tier 1 global inventories but close to Tier 3 estimates. The use of survey-based gridded N-input data contributes 58% of this emission reduction, the rest being explained by the use of observation-based non-linear EFs. We conclude that upscaling N₂O emissions from site-level observations to global croplands provides a new benchmark for constraining IPCC Tier 1 and 3 methods. The detailed spatial distribution of emission data is expected to inform advancement towards more realistic and effective mitigation pathways.

Keywords: agricultural soils; emission factor; emission inventories; flux upscaling; nitrous oxide; temporal trend.

Grants and funding

P 29130/FWF_/Austrian Science Fund FWF/Austria