Where does nitrous oxide come from, one of the main greenhouse gases emitted into the atmosphere ?

Where does nitrous oxide come from, one of the main greenhouse gases emitted into the atmosphere ?

Nitrous oxide is the third most common greenhouse gas of anthropogenic origin emitted into the atmosphere. zhongguo/Getty Images

In 2023, emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N₂O) continued to reach significant levels in the atmosphere, as this is demonstrated by a recent report from the American Oceanic and Atmospheric Observation Agency. While carbon dioxide and methane receive a lot of media coverage, nitrous oxide is more discreet. However, it is also a powerful greenhouse gas.

We know that the year 2023 was the hottest in centuries in the world. But another worrying record continues to rise, according to American scientists from the National Oceanic and Atmospheric Administration (NOAA). This time, it concerns greenhouse gas emissions generated by human activities.

"Although the increase in the three heat-trapping gases recorded in air samples collected by NOAA's Global Monitoring Laboratory (GML) in 2023 has not not been as significant as the record jumps observed in recent years, it is in line with the strong increases observed over the last decade", specify the researchers.

According to their estimates, the concentration of CO2 on the surface of the globe, calculated on average over the 12 months of 2023, was 419.3 parts per million (ppm), an increase of 2.8 ppm during the year. "This is the twelfth consecutive year that CO2 has increased by more than 2 ppm, continuing the highest rate of sustained CO2 increase over 65 years of monitoring ", notes NOAA, specifying that atmospheric CO2 is now 50% higher than pre-industrial levels. Methane would be responsible for 1922 parts per billion (ppb) emitted into the atmosphere.

Much more powerful warming power than CO2

With 336.7 ppb in 2023, nitrous oxide represents the third greenhouse gas of anthropogenic origin most emitted into the atmosphere. According to NOAA, its emissions into the atmosphere are 25% higher than the pre-industrial level (270 ppb). Also known as nitrous oxide, or more colloquially as “laughing gas”, nitrous oxide is naturally produced by soils and oceans. But around a third of its emissions are also linked to human activity, in particular to agricultural activities and more precisely to the use of nitrogen fertilizers, slurry and manure.

Less present in the atmosphere than carbon dioxide and methane, its warming power is however the most powerful of the three: 25 times more than methane and nearly 300 times more than carbon dioxide ! In addition to contributing to global warming, it contributes to deepening the hole in the ozone layer, as several studies have suggested. Research, published in 2009 in the journal Science, suggests in particular that "reducing nitrous oxide emissions would make it possible to accelerate the re-establishment of the hole in the layer ozone and reduce anthropogenic climate forcing".

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