Data-driven estimates of global nitrous oxide emissions from croplands. Issue 2 (11th July 2019)

• Record Type: Journal Article
• Authors: Wang, Qihui; Zhou, Feng; Shang, Ziyin; Ciais, Philippe; Winiwarter, Wilfried; Jackson, Robert B; Tubiello, Francesco N; Janssens-Maenhout, Greet; Tian, Hanqin; Cui, Xiaoqing; Canadell, Josep G; Piao, Shilong; Tao, Shu
• Is Part Of: National science review. Volume 7:Issue 2(2020)
• Page Start: 441
• Page End: 452
• Publication Date: 2019-07-11
• Subjects: nitrous oxide -- agricultural soils -- flux upscaling -- emission factor -- emission inventories -- temporal trend; Science -- Periodicals; 505
• DOI: 10.1093/nsr/nwz087
• Languages: English
• ISSNs: 2095-5138

Abstract

Abstract: Croplands are the single largest anthropogenic source of nitrous oxide (N2 O) 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-N2 O 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 N2 O 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.