Greenhouse Gases from United States 'Corn Belt' Grossly Underestimated

First Posted: Jul 29, 2015 09:40 AM EDT

It turns out that estimates for house much greenhouse gas the "corn belt" in the United States has been producing have been far too low. Scientists have found that the central U.S. estimates for nitrous oxide production have been too low by as much as 40 percent.

Nitrous oxide emissions are measured at the University of Minnesota Tall Tower Trace Gas Observatory, which provides a top-down constraint on regional emissions. Emissions are also calculated by combining on-the-ground (bottom-up) measurements within the region. This allows researchers to keep track of emissions and inform strategies for reducing nitrous oxide loss from agricultural lands.

With that said, it appears as if estimates have been far too long. The researchers found that there were discrepancies between bottom-up emission measurements and those taken from the air. These discrepancies could actually be attributed to variations in the size and flow of streams and rivers. By taking the impact of this water flow into account, the scientists could more accurately estimate and mitigate increased concentrations of nitrous oxide.

Interestingly, the researchers found that nitrous oxide emissions from rivers have been underestimated by as much as nine-fold. By properly accounting for these emissions, the scientists were able to resolve the difference between top-down and bottom-up emissions.

"Nitrous oxide emissions from rivers have been an overlooked and uncertain source because the variability in stream sizes and land-use types has made an accurate estimation difficult," said Peter Turner, one of the researchers, in a news release. "We identified an important relationship between the size of the stream and its potential to emit nitrous oxide that can be used to scale up emission estimates. Understanding the riverine nitrous oxide source is an important step forward for understanding the global nitrous oxide budget."

The findings are published in the journal Proceedings of the National Academy of Sciences.

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