Laughing gas rise leaves climate science anxious

Spreading fertiliser: A rural English scene − and a climate problem? Image: By Andrew Smith/Farmland above Aldbourne, via Wikimedia Commons

Atmospheric levels of laughing gas are on the increase, thanks to agriculture. This is no joke for climate change.

LONDON, 14 October, 2020 − If humans are to meet the global heating limits set by international agreement in 2015, they will have to think very hard about the effect of the supper table menu on laughing gas, more formally known as nitrous oxide.

That is because food production depends heavily on nitrogen fertilisers. But greenhouse gas emissions driven by agriculture are increasing atmospheric levels of nitrous oxide (N2O).

This is a greenhouse gas − popularly known as “laughing gas” − that is 300 times more potent than carbon dioxide, and it tends to stay in the atmosphere, driving up the thermometer, for at least 100 years. And in the 200 years since the start of the Industrial Revolution, atmospheric levels of nitrous oxide have risen by 20%, and are still rising.

Nitrous oxide is one of the six greenhouse gases identified in the Kyoto Protocol, the pioneering global climate agreement, as a danger whose emissions should be reduced by all its signatories.

The ratio of N2O to other gases is tiny, a thousand times lower than carbon dioxide, for instance, but an increase can still make a significant difference. In 1750 the ratio stood at 270 parts per billion. In 2018 it had reached 331 ppb, with the fastest growth all in the last 50 years, thanks to humankind’s demand for food.

“There is a conflict between the way we are feeding people and stabilising the climate”

And this, say 57 scientists from 14 nations in a report in the journal Nature, now threatens to eliminate any hope of containing global heating to “well below” 2°C by the year 2100. This is the target set in the Paris Agreement in 2015 by 195 nations.

Right now, the world has already warmed by 1°C in the last century and on all the evidence so far it is heading by the end of the century to be at least 3°C hotter than the average for most of the last 10,000 years of human history.

“The dominant driver of the increase in atmospheric nitrous oxide comes from agriculture, and the growing demand for food and feed for animals will further increase global nitrous oxide emissions,” said Hanqin Tian, of Auburn University’s School of Forestry and Wildlife Sciences in Alabama in the US. “There is a conflict between the way we are feeding people and stabilising the climate.”

He and his colleagues call their research an inventory of the traffic in nitrous oxide from human and from natural sources. The most significant human source is the fertiliser added to croplands.

They found that the highest growth in nitrous oxide emissions came from emerging economies in East Asia, South Asia, Africa and South America, from synthetic fertilisers and from livestock manure. In the course of the next few decades global population will soar, and so will the demand for food.

Total rethink

Researchers have consistently argued for a new approach to agriculture,  with ever-greater emphasis on plant-based diets, as a way to help contain climate change on a scale that is likely to actually threaten global food security.

“Europe is the only region in the world that has successfully reduced nitrous oxide emissions over the past two decades,” said Robert Jackson,  of Stanford University in the US, who chairs the Global Carbon Project.

“Industrial and agricultural policies to reduce greenhouse gases and air pollution and to optimise fertiliser use efficiencies have proven to be effective. Still, further efforts are required, in Europe as well as globally.”

And another author, Josep Canadell of Australia’s Commonwealth Scientific and Industrial Research Organisation, said: “This new analysis calls for a full rethink in the ways we use and abuse nitrogen fertilisers globally and urges us to adopt more sustainable practices in the way we produce food,  including the reduction of food waste.” − Climate News Network