Nitrous oxide: The unnoticed greenhouse gas

When it comes to greenhouse gases, most global focus is on carbon dioxide and methane. Nitrous oxide, the third-most-emitted greenhouse gas, seems to go unnoticed, despite its gut punch to the climate. Known as laughing gas, nitrous oxide is almost 300 times as potent a greenhouse gas as CO 2 ; it also depletes the stratospheric ozone layer. Nitrous oxide emissions from human activities have gone up by 30% since 1980, faster than scientists had previously assumed, according to a recent study in Nature . Yet, N 2 O has received little attention in international climate or ozone treaties. That’s mainly because agriculture is responsible for over two-thirds of N 2 O emissions. Both nitrogen-based fertilizer and manure emit the gas as they break down. Policy makers and farm lobbies make the case that these agricultural emissions are difficult to monitor. But emissions by the chemical industry, the next-biggest source,