 | Ozone threat identified
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Sept. 11, 2009 - In a new study by NOAA scientists, nitrous oxide has been identified as the largest ozone-depleting substance emitted through human activities. |
| Earth as seen by Apollo 17 astronauts | |
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ACCORDING TO NOAA, nitrous oxide is emitted from natural sources and as a byproduct of agricultural fertilization and other industrial processes. Nitrous oxide is emitted from livestock manure, sewage treatment, combustion and certain 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. About one-third of global nitrous oxide emissions are from human activities.
In nature, bacteria in soil and the oceans break down nitrogen-containing compounds, releasing nitrous oxide. Nitrous oxide, like chlorofluorocarbons (CFCs), is stable when emitted at ground level, but breaks down when it reaches the stratosphere to form other gases, called nitrogen oxides, that trigger ozone-destroying reactions.
“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,” A. R. Ravishankara, Ph.D., lead author of the study, said.
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, [blue]ebb[/blue] in the atmosphere, the study found that nitrous oxide will remain a significant ozone-destroyer. Today, nitrous oxide emissions from human activities are more than twice as high as the next leading ozone-depleting gas.
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.
Scientists expect nitrous oxide to remain the largest ozone-depleting substance through the 21st Century.
NOAA: National Oceanic and Atmospheric Administration
