Planet-warming nitrous oxide (N2O) emissions grew by 40 per cent between 1980 and 2020, with China being the largest emitter, followed by India and the US, according to a new report.

The study by the Global Carbon Project, a network of climate scientists, also said that 74 per cent of the nitrous oxide emissions in the past decade came from the use of nitrogen fertilizers and animal manure in agriculture.

The top 10 emitters are China, India, the US, Brazil, Russia, Pakistan, Australia, Indonesia, Turkey, and Canada, it said.

Nitrous oxide is the third most significant greenhouse gas after carbon dioxide and methane and is 273 times more potent than CO2 over 100 years.

The increase in greenhouse gases has already raised the Earth's average surface temperature by 1.15 degrees Celsius compared to the 1850-1900 average. Anthropogenic nitrous oxide emissions contribute to about 0.1 degrees of this warming.

In 2022, the concentration of nitrous oxide in the atmosphere reached 336 parts per billion, 25 per cent higher than in 1850-1900, significantly surpassing the predictions of the Intergovernmental Panel on Climate Change.

Agricultural emissions were 8 million metric tonnes in 2020, a 67 per cent increase from the 4.8 million metric tonnes in 1980, according to a study published in the journal Earth System Science Data.

Scientists suggest that to keep the global temperature rise below 2 degrees Celsius, as set by the Paris Agreement, nitrous oxide emissions from human activities must decrease by at least 20 per cent from 2019 levels by 2050.

"Nitrous oxide emissions from human activities must decline to limit global temperature rise to 2 degrees Celsius," said the report’s lead author, Hanqin Tian, the Schiller Institute Professor of Global Sustainability at Boston College.

"Reducing nitrous oxide emissions is the only solution since there are currently no technologies to remove it from the atmosphere," he said.

In 1980, farmers used 60 million metric tonnes of commercial nitrogen fertilizers. By 2020, the usage had increased to 107 million metric tonnes. Animal manure contributed 101 million metric tonnes in 2020, making the total usage 208 million metric tonnes.

The scientists also pointed out that the continuous rise in a greenhouse gas with a global warming potential about 300 times greater than carbon dioxide poses serious threats to the planet.

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