We synthesized N₂O 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 N₂O 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.

中文翻译：

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基于自下而上和自上而下方法的北美一氧化二氮排放量和不确定性：为未来研究和国家清单提供信息

我们使用 1980-2016 年的 17 个自下而上 (BU) 估计值和 1998 年至 2016 年的五个自上而下 (TD) 估计值合成了北美的N ₂ O 排放量。基于 BU 的总排放量显示由于美国农业而略有增加，而在 TD 估计中没有显示一致的趋势。2007-2016 年期间，北美 N ₂ O 排放量估计为 1.7 (1.0-3.0) Tg N yr ^-1 (BU) 和 1.3 (0.9-1.5) Tg N yr ^-1(TD)。人为排放量是来自土壤和水的自然通量的两倍。直接农业和工业活动占人为排放总量的 68%，其中 71% 来自美国因素）和第 3 层（基于过程的建模）方法。相反，我们估算的加拿大和墨西哥的农业排放量是各自国家温室气体清单的两倍。