Nitrous dioxide, popularly known as 'laughing gas', has now become the largest ozone-depleting substance emitted through human activities, says a new study.
The study was authored by A.R. Ravishankara, J.S. Daniel and Robert W. Portmann of the NOAA Earth System Research Laboratory (ESRL) chemical sciences division.
For the first time, this study has evaluated nitrous oxide emissions from human activities in terms of their potential impact on Earth's ozone layer.
As chlorofluorocarbons (CFCs), which have been phased out by international agreement, ebb in the atmosphere, nitrous oxide will remain a significant ozone-destroyer, the study found.
Today, nitrous oxide emissions from human activities are more than twice as high as the next leading ozone-depleting gas.
Nitrous oxide is emitted from natural sources and as a byproduct of agricultural fertilization and other industrial processes.
Calculating the effect on the ozone layer now and in the future, NOAA researchers found that emissions of nitrous oxide from human activities erode the ozone layer and will continue to do so for many decades.
ESRL tracks the thickness of the ozone layer, as well as the burden of ozone-depleting compounds in the atmosphere. It maintains a large portion of the world air sampling and measurement network.
NOAA scientists also conduct fundamental studies of the atmosphere and atmospheric processes to improve understanding of ozone depletion and of the potential for recovery the ozone layer.
"The dramatic reduction in CFCs over the last 20 years is an environmental success story. But manmade nitrous oxide is now the elephant in the room among ozone-depleting substances," said Ravishankara, lead author of the study and director of the ESRL Chemical Sciences Division in Boulder, Colorado.
The ozone layer serves to shield plants, animals and people from excessive ultraviolet light from the sun.
Thinning of the ozone layer allows more ultraviolet light to reach the Earth's surface where it can damage crops and aquatic life and harm human health.
Though the role of nitrous oxide in ozone depletion has been known for several decades, the new study is the first to explicitly calculate that role using the same measures that have been applied to CFCs, halons and other chlorine- and bromine-containing ozone-depleting substances.
According to scientists, nitrous oxide is also a greenhouse gas, so reducing its emission from manmade sources would be good for both the ozone layer and climate.