Scientists at the University of California, Davis, have developed a way to more accurately forecast nitrogen’s effects on the climate cycle. Incorporating this method shows the planet may be headed for a warmer future than was previously thought, according to research published today in the journal Nature Climate Change.

According to the researchers, models used by the Intergovernmental Panel on Climate Change until now have not provided realistic predictions of nitrogen emissions from the land to the air and water. Of the 12 climate models used by the IPCC, only one included nitrogen, and that model was not tracing nitrogen correctly.

“Our benchmarking methods will provide a way for all the models to include nitrogen, to communicate with each other, and to reduce their overall uncertainty,” said lead author Benjamin Houlton, a professor in the UC Davis Department of Land, Air and Water Resources. “Including this information will likely reveal that the climate system is more sensitive than we anticipate, and it likely will be a warmer world than we think.”

Tracing nitrogen’s journey

The scientists identified the isotopic “fingerprints” of nitrogen, tracing its journey to model how nitrogen moves through ecosystems and how it escapes to the air or water. The benchmarking technique is now being put into global models used by the IPCC.

[30 second audio clip: Nitrogen: Too much of a good thing.]

Nitrogen is a critical component of climate change. It determines how much carbon dioxide emissions natural ecosystems can absorb, and it directly warms the climate as nitrous oxide in the atmosphere. It occurs naturally in the air and water and also enters the environment through man-made agricultural fertilizers.

The benchmarking technique Houlton and his colleagues developed will help examine the fate of nitrogen fertilizers in the environment as well as the climate impacts of nitrogen.

“Nitrogen is a challenge facing humanity,” Houlton said. “It’s becoming too much of a good thing. We will hear more and more about nitrogen’s impact on human health and the environment in the future, but developing a more sophisticated scientific understanding of the nitrogen cycle is essential to provide policymakers, stakeholders and the public better information to make decisions.”

The study’s co-authors include former UC Davis postdoctoral students Alison Marklein and Edith Bai. It received funding from the Andrew W. Mellon Foundation and the National Science Foundation.