Magnitude and uncertainty of nitrous oxide emissions from North America
based on bottom-up and top-down approaches: Informing future research
and national inventories
Abstract
We synthesized N2O emissions over North America using 17
bottom-up (BU) estimates from 1980-2016 and five top-down (TD) estimates
from 1998-2016. 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 larger than 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 based on
tier 1 approaches.
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