Science Daily: Nitrous oxide has now become the largest ozone-depleting substance emitted through human activities, and is expected to remain the largest throughout the 21st century, NOAA scientists say in a new study.
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.
The study, authored by A.R. Ravishankara, J.S. Daniel and Robert W. Portmann of the NOAA Earth System Research Laboratory (ESRL) chemical sciences division, appears online today in the journal Science. 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, Colo.