Magnitude and Uncertainty of Nitrous Oxide Emissions From North America Based on Bottom‐Up and Top‐Down Approaches: Informing Future Research and National Inventories
Rongting Xu, Hanqin Tian, Neil Pan, Rona L. Thompson, Josep G. Canadell, Eric A. Davidson, C. D. Nevison, Wilfried Winiwarter, Hao Shi, Shufen Pan, Jinfeng Chang, Philippe Ciais, Shree R. S. Dangal, Akihiko Ito, Robert B. Jackson, Fortunat Joos, Ronny Lauerwald, Sebastian Lienert, Taylor Maavara, Dylan B. Millet, Peter A. Raymond, Pierre Regnier, Francesco N. Tubiello, Nicolas Vuichard, Kelley C. Wells, Chris Wilson, Jia Yang, Yitong Yao, Sönke Zaehle, Feng Zhou
Abstract
Abstract We synthesized N 2 O emissions over North America using 17 bottom‐up (BU) estimates from 1980–2016 and five top‐down (TD) estimates from 1998 to 2016. The BU‐based total emission shows a slight increase owing to U.S. agriculture, while no consistent trend is shown in TD estimates. During 2007–2016, North American N 2 O emissions are estimated at 1.7 (1.0–3.0) Tg N yr −1 (BU) and 1.3 (0.9–1.5) Tg N yr −1 (TD). Anthropogenic emissions were twice as large as natural fluxes from soil and water. Direct agricultural and industrial activities accounted for 68% of total anthropogenic emissions, 71% of which was contributed by the U.S. Our estimates of U.S. agricultural emissions are comparable to the EPA greenhouse gas (GHG) inventory, which includes estimates from IPCC tier 1 (emission factor) and tier 3 (process‐based modeling) approaches. Conversely, our estimated agricultural emissions for Canada and Mexico are twice as large as the respective national GHG inventories.