Miller Magazine Issue: 131 November 2020

30 NEWS MILLER / November 2020 Rising anthropogenic nitrous oxide emissions are jeopardizing climate goals and the Paris Accord, a study published in Nature and led by an Auburn University researcher has found. Breakthrough study confirms global food production poses an increasing climate threat The significant use of nitrogen fertilizers in the produ- ction 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 global nitrous oxide budget for 2007-16. The co- lored arrows represent nitrous oxide fluxes (in Tg N yr−1 for 2007-16) as follows: yellow, emissions from anthro- pogenic sources (agriculture and waste water, biomass burning, fossil fuel and industry, and indirect emission); green, emissions from natural sources; blue, atmosphe- ric chemical sink; and other fluxes, such as lightning and atmospheric production, soil surface sink, climate chan- ge, increasing carbon dioxide and deforestation. This finding is part of a study co-led by Professor Hanqin Tian, director of the International Center for Climate and Global Change Research at Auburn Uni- versity's School of Forestry and Wildlife Sciences and an Andrew Carnegie Fellow. The study was published today in Nature, the world's most highly cited interdisciplinary science journal. Tian co-led an international consortium of scientists from 48 research institutions in 14 countries under the umbrella of the Global Carbon Project and the Internati- onal Nitrogen Initiative. The objective of the study, titled "A comprehensive quantification of global nitrous oxide sources and sinks," was to produce the most comprehen- sive assessment to date of all sources and sinks of the potent greenhouse gas nitrous oxide. Tian's Auburn colleagues including Professor Shufen Pan, postdoctoral fellows Rongting Xu, Hao Shi and Yu- anzhi Yao and graduate student Naiqing Pan served as co-authors among an international research team of 57 scientists. The study points to an alarming trend affecting cli- mate 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 ac- tivities. "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 incre- ase global nitrous oxide emissions," Tian said. "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 ad- ditions for food production further enhancing emissions from agriculture. Warmer temperatures tend to increase nitrous oxide emissions. The study also determined that the largest contribu- tors 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, the study found. The highest growth rates in emissions are found in emerging economies, particularly Brazil, China and In- dia, 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 nit- rous oxide emissions are not compatible with pathways consistent to achieve the climate goals of the Paris Cli- mate Agreement, or the Paris Accord. Signed by 195 nations, the agreement aims to strengt- hen the global response to the threat of climate change by keeping a global temperature rise in the 21st century well below 2 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 tempe- rature increases above 3 degrees Celsius by the end of this century, twice the temperature target of the Paris Accord,"