Nitrous oxide (N2O) is one of the lesser known greenhouse gases. And yet, a recent study highlights an increase in emissions synonymous with a gloomy climate future. We are still talking about a gas 300 times warmer than carbon dioxide!
First of all, it should be remembered that the objectives of the Paris Climate Agreement are to limit warming to 2 °C or even 1.5 °C. To do this, we would have to limit our carbon dioxide (CO2) and methane (CH4) emissions, which governments are struggling to do. However, a study published in the journal Nature on October 7, 2020 looks at a lesser-known greenhouse gas: nitrous oxide (N2O).
Researchers at Auburn University in the United States estimate that N2O has a warming power 300 times that of CO2. As for the lifetime in the atmosphere, it is 120 years for N2O compared to 100 years for CO2. The study directors pondered a simple question: Should we be concerned about our nitrous oxide emissions? The study presents the most comprehensive assessment of all natural and man-made sources of nitrous oxide in the world. According to the results, emissions are increasing faster than IPCC experts thought.
The study suggests an increase in average temperature exceeding 3 °C. The level of nitrous oxide in the atmosphere has increased by 20% compared to the pre-industrial era. In 1750, this rate was 270 parts per billion (ppb) compared to 331 ppb in 2018. During the last four decades, human-made emissions have increased by 30%. However, N2O is one of the most harmful agents for the ozone layer.
The sector most responsible for NO2 emissions is none other than agriculture, more specifically animal husbandry and crops used for animal feed. This is linked to an overuse of nitrogen fertilizers and poor management of droppings and crop residues. This sector is responsible for 85% of nitrous oxide emissions. In countries such as the United States, China and India, emissions come mainly from synthetic fertilizers. In South America and Africa, livestock manure is also an issue. In Europe, on the other hand, emissions were reduced thanks to measures to optimize the efficiency of fertilizer use.
Finally, scientists also point to an emerging N2O-climate feedback. This results from the interactions between nitrogen additions to crops (food production) and global warming. Among the solutions, researchers are thinking of limiting meat consumption, diversifying gardening and, of course, developing eco-friendly animal or plant fertilizers.