The colossal amount of nitrogen used as fertilizer in agriculture is leading to an increase in emissions of nitrous oxide, a lesser-known greenhouse gas that contributes to climate change and the depletion of the ozone layer. Nitrous oxide emissions are increasing at a rate of about 2% per decade, and in 2018 the gas’s concentration in the atmosphere was about 22% above pre-industrial levels, according to a study published today in Nature, the first to do a thorough accounting of atmospheric nitrous oxide. The paper was five years in the making, and involved 48 research institutions from around the world.
“Now that we have started to draw pathways to net zero emissions, we must understand all greenhouse gases,” said Pep Canadell, co-author and executive director of the Global Carbon Project. “It has taken us a very long time to understand how nitrous oxide emissions work, but we have learnt that emissions from natural sources haven’t changed, while human emissions have increased a lot.”
Nitrous oxide, or N₂O, is the third-most abundant greenhouse gas after carbon dioxide and methane. The gas has about 300 times more warming power than carbon dioxide over the course of a century, and stays in the atmosphere warming the planet for 116 years. Unlike other gases that destroy the ozone layer, which protects Earth from ultraviolet radiation, its emissions haven’t been banned.