Peasant spraying fertiliser on rice during harvest time in Yunnan province, China.

A farmer fertilizes rice in Yunnan province, China. Emissions of the pollutant nitrous oxide have spiked in part because of fertilizer use in Asia and South America. Credit: Majority World/Universal Images Group/Getty

Environmental sciences

Pollutant’s accelerating emissions are an unwelcome surprise

Levels of nitrous oxide, which promotes global warming, are galloping upwards at a rate higher than previously estimated.

Global emissions of nitrous oxide, a potent greenhouse gas, seem to be rising much faster than scientists have thought.

The gas, which destroys ozone in the stratosphere, is a by-product of the use of nitrogen-based fertilizers, which are commonly applied to farm fields. Rona Thompson at the Norwegian Institute for Air Research in Kjeller and her colleagues combined data from a global network of observations with atmospheric transport models, to calculate the rate of nitrous oxide emissions from 1998 to 2016.

The team found that during that period, the rise in global emissions was almost twice as large as previous estimates, which were based mainly on statistics about fertilizer usage. Emissions from East Asia and South America account for the bulk of the estimated increase.

Nitrous oxide emissions rise disproportionally in response to nitrogen use in agriculture, the authors conclude. Reducing global emissions would require more efficient fertilizer application and, ultimately, changes in human diet, they say.