Magnitude and Uncertainty of Nitrous Oxide Emissions From North America Based on Bottom-Up and Top-Down Approaches: Informing Future Research and National Inventories

Authors

R. Xu, Auburn University
Hanqin Tian, Auburn UniversityFollow
N. Pan, Auburn University
R. L. Thompson, Norsk institutt for luftforskning
J. G. Canadell, CSIRO Oceans and Atmosphere
E. A. Davidson, University of Maryland Center for Environmental Science
C. Nevison, University of Colorado Boulder
W. Winiwarter, International Institute for Applied Systems Analysis, Laxenburg
H. Shi, Auburn University
S. Pan, Auburn University
J. Chang, College of Environmental and Resource Sciences, Zhejiang University
P. Ciais, Commissariat a L'Energie Atomique CEA
Shree Dangal, University of Nebraska-LincolnFollow
A. Ito, National Institute for Environmental Studies of Japan
R. B. Jackson, Stanford University
F. Joos, University of Bern, Institute of Applied Physics
R. Lauerwald, Universite Paris-Saclay
S. Lienert, University of Bern, Institute of Applied Physics
T. Maavara, Yale University
D. B. Millet, University of Minnesota Twin Cities
P. A. Raymond, Yale University
P. Regnier, Université Libre de Bruxelles
F. N. Tubiello, Food and Agriculture Organization of the United Nations
N. Vuichard, Commissariat a L'Energie Atomique CEA
K. C. Wells, University of Minnesota Twin Cities
C. Wilson, University of Leeds
J. Yang, College of Forest Resources
Y. Yao, Auburn University
S. Zaehle, Max Planck Institute for Biogeochemistry
F. Zhou, Peking University

ORCID IDs

R. Xu https://orcid.org/0000-0001-7292-9271

H. Tian https://orcid.org/0000-0002-1806-4091

R. L. Thompson https://orcid.org/0000-0001-9485-7176

J. G. Canadell https://orcid.org/0000-0001-9485-7176

E. A. Davidson https://orcid.org/0000-0002-8525-8697

C. Nevison https://orcid.org/0000-0002-7157-092X

W. Winiwarter https://orcid.org/0000-0001-7131-1496

S. Pan https://orcid.org/0000-0001-7920-1427

P. Ciais https://orcid.org/0000-0001-8560-4943

S. R. S. Dangal https://orcid.org/0000-0001-9529-8206

A. Ito https://orcid.org/0000-0001-5265-0791

R. B. Jackson https://orcid.org/0000-0001-8846-7147

F. Joos https://orcid.org/0000-0002-9483-6030

R. Lauerwald https://orcid.org/0000-0001-5554-0897

S. Lienert https://orcid.org/0000-0003-1740-918X

T. Maavara https://orcid.org/0000-0001-6677-9262

D. B. Millet https://orcid.org/0000-0003-3076-125X

P. A. Raymond https://orcid.org/0000-0002-8564-7860

N. Vuichard https://orcid.org/0000-0002-3397-7948

K. C. Wells https://orcid.org/0000-0003-3025-6878

C. Wilson https://orcid.org/0000-0001-8494-0697

S. Zaehle https://orcid.org/0000-0001-5602-7956

F. Zhou https://orcid.org/0000-0001-6122-0611

Document Type

Article

Date of this Version

12-16-2021

Citation

Xu, R., Tian, H., Pan, N., Thompson, R. L., Canadell, J. G., Davidson, E. A., Dangal, S.R.S., et al. (2021). Magnitude and uncertainty of nitrous oxide emissions from North America based on bottom-up and top-down approaches: Informing future research and national inventories. Geophysical Research Letters, 48, e2021GL095264.

doi:10.1029/2021GL095264

Comments

© 2021. American Geophysical Union. Used by permission.

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 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.

Plain Language Summary Nitrous oxide (N₂O) is the third most important greenhouse gase (GHG) after CO₂ and CH₄ causing global warming. Among world regions, North America (defined herein as U.S., Canada, and Mexico) is the second largest source of N₂O emissions globally, and previous source estimates for this region vary widely. This study aims to provide a comprehensive N₂O assessment over North America including all available estimates based on a number of approaches. We report total emissions, and emissions from four anthropogenic source sectors, over the past four decades. Agriculture and industry are two major N₂O sources in North America. Our results show a minor increase in the total N₂O emission due to agricultural trends in the U.S. Our bottom-up estimate of U.S. agSricultural N₂O emissions are close to those in the EPA national GHG inventory that includes both empirical and model results. The high consistency suggests the need to take process-based modeling results into account for future national GHG inventories.