A Forgotten Greenhouse Gas: How scientists have underestimated the impacts of nitrous oxide emissions

February 2, 2021

A Forgotten Greenhouse Gas: How scientists have underestimated the impacts of nitrous oxide emissions

Image courtesy of NASA Earth Observatory (Wikimedia Commons).

While the anthropogenic element of climate change remains a hotly politicized topic and the crisis itself becomes ever more dire, a coalition of scientists spanning a range of disciplines and institutions report that a less frequently mentioned greenhouse gas may have a greater impact on climate change than previously thought.

The term “greenhouse gas” usually brings to mind carbon dioxide or methane—and for good reason. Combined, these two gases accounted for seventy-six percent of all greenhouse gases emitted globally in 2010. As such, previous research and discussion on climate change and greenhouse gases have centered around carbon dioxide and methane, leaving other important gases, like nitrous oxide, out of the conversation. To address this gap in understanding, a multinational, multi-disciplinary consortium of researchers combined local and national N2O measurements to build the most complete picture of nitrous oxide levels to date.

In a paper published this October in Nature, this team of scientists, including Taylor Maavara, a Hutchinson postdoctoral fellow at Yale’s School of Forestry and Environmental Studies, presented the most comprehensive global study of nitrous oxide (N2O) levels to date. The study also placed a larger emphasis on Maavara’s area of focus: inland water bodies, such as lakes, rivers, reservoirs, and estuaries (where a river meets the ocean). Old budgets often glossed over such bodies, focusing mainly on oceans and the continents; however, “inland water bodies are actually really reactive…and once you start adding up all the rivers, lakes, and reservoirs, it ends up being a lot, and folks have been neglecting that,” Maavara said.

Unfortunately, the results were not optimistic. “[The study] showed that it’s worse than the worse-case scenario, in terms of how fast the N2O emissions are going up,” Maavara said. The rising emissions are strongly connected to increasing agricultural outputs to support growing population sizes, posing a dilemma for policymakers. In addition, newly constructed dams in countries such as China, Brazil, and India may also play a role by altering the natural inland water bodies within the N2O cycle.

While the study’s language describes these results in the typical measured tone of many scientific reports, it brings with it the reality and urgency of the climate and greenhouse gas situation. With the combined results of the coalition painting an alarming picture of the current status of N2O levels—and no simple solution in sight—we are reminded of the importance of scientific transparency and broader conversations about climate change, greenhouse gases, and global warming.

Sources

1. Tian, H., Xu, R., Canadell, J.G. et al. A comprehensive quantification of global nitrous oxide sources and sinks. Nature 586, 248–256 (2020). https://doi.org/10.1038/s41586-020-2780-0

2. Interview with Dr. Taylor Maavara, Yale School of Forestry and Environmental Studies, Interview on 10/31/2020

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