Nitrous oxide, laughing gas, emissions up 40% in 40 years

New figures shows that nitrous oxide emissions have increased more than 40% over the last 40 years, including accelerated growth in 2020–2022.

The data is presented in the second Global Nitrous Oxide Budget, published in the journal Earth System Science Data. The first was published in 2020.

After carbon dioxide and methane, nitrous oxide (N­2O – also known as “laughing gas”) is the third most important greenhouse gas contributing to human-induced climate change. The gas remains in the atmosphere for more than 100 years and eats away at the ozone layer.

The main source of increased N2O in the atmosphere is agriculture, accounting for 74% of emissions. The gas is produced from nitrogen fertilisers and animal manure. Other human sources include burning of fossil fuels, waste and wastewater, and burning of biological matter.

Global Nitrous Oxide Budgets are a key part of greenhouse has assessments coordinated by the Global Carbon Project. The new paper is based on international research including researchers based at Australia’s national science agency, CSIRO.

“Growth rates over the past three years – from 2020–2022 – are 30% higher than any previously observed year since 1980,” says CSIRO scientist Dr Pep Canadell.

The report quantifies N2O sinks and sources in 21 natural and human categories.

“The once top emitter, Europe, has reduced its emissions since the 1980s by 31%, through industrial emission reductions,” says first author Dr Hanqin Tian from Boston College in the US. “However, emerging economies have grown in response to growing population and food demand.”

“The top 5 country emitters by volume of anthropogenic N₂O emissions in 2020 were China (16.7%), India (10.9%), USA (5.7%), Brazil (5.3%), and Russia (4.6%).”

Graph of nitrogen oxide levels
Graph of 2000 years of atmospheric nitrous oxide concentrations. Observations taken from ice cores and the atmosphere. © Bureau of Meteorology/CSIRO/Australian Antarctic Division.

Australia’s human-based N2O emissions have been stable over the last 2 decades.

“For net-zero emission pathways consistent with the Paris Agreement to stabilise global temperatures below 2°C, anthropogenic N₂O emissions need to decline on average by about 20% by 2050 from 2019 levels,” Canadell says.

Researchers at CSIRO and internationally are working on initiatives to reduce N2O emissions, including tackling nitrogen fertiliser emissions and studying the N2O footprint of the grains sector.

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