Research

The most comprehensive assessment of global sources and sinks of nitrous oxide

OCT . 12 2020
Peking University, October 12, 2020: Rising anthropogenic nitrous oxide emissions are jeopardizing climate goals and the Paris Accord, according to a new study published on October 7 in Nature (2020, 586: 248–256). Led by Auburn University under the umbrella of the Global Carbon Project and the International Nitrogen Initiative, the research was undertaken by an international consortium of 57 scientists from 14 countries and 48 research institutions, among which Peking University (PKU) plays an important role.
 
The significant use of nitrogen fertilizers in the production of food worldwide is increasing concentrations of nitrous oxide in the atmosphere—a greenhouse gas 300 times more potent than carbon dioxide—which remains in the atmosphere longer than a human lifetime.
 
The study points to an alarming trend affecting climate change: Nitrous oxide has risen 20 percent from pre-industrial levels, and its growth has accelerated over recent decades due to emissions from various human activities.
 
“The dominant driver of the increase in atmospheric nitrous oxide comes from agriculture, and the growing demand for food and feed for animals will further increase global nitrous oxide emissions,” explains study lead author Tian Hanqin, director of the International Center for Climate and Global Change Research at Auburn University. “There is a conflict between the way we are feeding people and stabilizing the climate.”
 
The researchers further identify an emerging cause of increased atmospheric nitrous oxide coming from the interaction between global warming and nitrogen additions for food production further enhancing emissions from agriculture. Warmer temperatures tend to increase nitrous oxide emissions.
 
The study also determined that the largest contributors to global nitrous oxide emissions come from East Asia, South Asia, Africa and South America.
 
“Emissions from synthetic fertilizers dominate releases in China, India and the U.S., while emissions from the application of livestock manure as fertilizer dominates releases in Africa and South America,” said Zhou Feng, an associate professor and co-author from PKU and one of steering committee member of GCP-INI Global N2O Budget Activity. “The highest growth rates in emissions are found in emerging economies, where crop production and livestock numbers have increased.”
 
The co-authors agreed that the most surprising result of the study was the finding that current trends in nitrous oxide emissions are not compatible with pathways consistent to achieve the climate goals of the Paris Climate Agreement, or the Paris Accord.
 
Signed by 195 nations, the agreement aims to strengthen the global response to the threat of climate change by keeping a global temperature rise in the 21st century well below two degrees Celsius above pre-industrial levels, and to pursue efforts to limit the temperature rise even further, to 1.5 degrees Celsius.
 
“Current emissions are on track to cause global temperature increases above 3 degrees Celsius by the end of this century, twice the temperature target of the Paris Accord,” said Robert Jackson, a professor and coauthor from Stanford University and chair of the Global Carbon Project.
 
However, opportunities to reduce nitrous oxide emissions do exist, said Wilfried Winiwarter, a senior research scholar with the International Institute of Applied Systems Analysis in Austria and former director of the International Nitrogen Initiative and its European center.
 
“Europe is the only region in the world that has successfully reduced nitrous oxide emissions over the past two decades,” Winiwarter said. “Industrial and agricultural policies to reduce greenhouse gases and air pollution and to optimize fertilizer use efficiencies have proven to be effective. Still, further efforts will be required, in Europe as well as globally.”
 
Rona Thompson, a senior scientist from the Norwegian Institute for Air Research, was another study co-leader.
 
“This study shows that we now have a comprehensive understanding of the nitrous oxide budget, including climate impacts,” Thompson said. “We are able to assess and quantify measures to reduce nitrous oxide emissions, and many of these measures will also improve water and air quality, benefiting both human health and ecosystems.”
 
Study co-leader Josep “Pep” Canadell, chief scientist in the Climate Science Center at the Australia-based Commonwealth Scientific and Industrial Research Organisation and executive director of the Global Carbon Project, agreed the research is significant and urgent.
 
“This new analysis calls for a full-scale rethink in the ways we use and abuse nitrogen fertilizers globally and urges us to adopt more sustainable practices in the way we produce food, including the reduction of food waste,” Canadell said. “These findings underscore the urgency and opportunities to mitigate nitrous oxide emissions worldwide to avoid the worst of climate impacts.”
 
Francesco Tubiello, a senior statistician and team leader for Agri-Environmental Statistics in the Food and Agriculture Organization of the United Nations, added, “Many of the actions to improve nitrogen use efficiency and improve crop and livestock productivity, required now to begin reducing these emissions, are also needed to achieve sustainable and productive agriculture under the United Nation’s 2030 Agenda for Sustainable Development Goals.”
 
Sources: School of Forestry and Wildlife Sciences, Auburn University, College of Urban and Environmental Sciences, Peking University