| 1 | Data-driven estimates of global nitrous oxide emissions from croplands显示文摘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. | 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 | 2020 | National Science Review2020，7，2： | 7 |
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