Nitrous oxide (N2O) has a global warming potential that is 300 times that of carbon dioxide on a 100-y timescale, and is of major importance for stratospheric ozone depletion. The climate sensitivity of N2O emissions is poorly known, which makes it difficult to project how changing fertilizer use and climate will impact radiative forcing and the ozone layer. Analysis of 6 y of hourly N2O mixing ratios from a very tall tower within the US Corn Belt—one of the most intensive agricultural regions of the world—combined with inverse modeling, shows large interannual variability in N2O emissions (316 Gg N2O-N·y−1 to 585 Gg N2O-N·y−1). This implies that the regional emission factor is highly sensitive to climate. In the warmest year and spring (2012) of the observational period, the emission factor was 7.5%, nearly double that of previous reports. Indirect emissions associated with runoff and leaching dominated the interannual variability of total emissions. Under current trends in climate and anthropogenic N use, we project a strong positive feedback to warmer and wetter conditions and unabated growth of regional N2O emissions that will exceed 600 Gg N2O-N·y−1, on average, by 2050. This increasing emission trend in the US Corn Belt may represent a harbinger of intensifying N2O emissions from other agricultural regions. Such feedbacks will pose a major challenge to the Paris Agreement, which requires large N2O emission mitigation efforts to achieve its goals.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Nov 7 2017|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. This research was partially supported by the US Department of Agriculture (USDA) (Grant 2013-67019-21364), USDA Agricultural Research Service, NOAA (Grant NA13OAR4310086), US National Science Foundation (Grant 1640337), Minnesota Corn Growers Association (Grant 4118-15SP), and the Minnesota Supercomputing Institute for Advanced Computational Research (https://www.msi.umn.edu/). We acknowledge the support of an MnDrive PhD fellowship (to Z.C.).
- Atmospheric inversion
- Climate change
- Nitrous oxide emissions
- Synthetic nitrogen