August 28, 2009

Nitrous Oxide Depleting Ozone Layer

NOAA has released the first-ever study of the climate impacts of the man-made substance, nitrous oxide.

Researchers A.R. Ravishankara, J.S. Daniel and Robert W. Portmann of the National Oceanic and Atmospheric Administration's Earth System Research Laboratory (ESRL), said that nitrous oxide, also known as laughing gas, has become the largest ozone-depleting substance emitted through human activities.

Additionally, the gas is expected to continue its status through the 21st century.

"Nitrous oxide emissions from human activities are more than twice as high as the next leading ozone-depleting gas," researchers noted.

The study is published in the journal Science.

Nitrous is emitted naturally as well as a byproduct of agricultural fertilization and other industrial processes. About 10 million tons "“ one third of global emissions "“ come from human activities each year.

Ravishankara and Portmann said that nitrous oxide emissions are whittling down the ozone layer and will continue to do so for many decades.

Ravishankara called man-made nitrous oxide "the elephant in the room among ozone-depleting substances."

Scientists have known about the ozone-depleting impact of nitrous oxide for many decades. However, the NOAA study is the first to calculate that impact in comparison with measures that have been used with chlorofluorocarbons (CFCs), halons and other chlorine- and bromine-containing ozone-depleting substances.

"Nitrous oxide, like 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," researchers said.

CFCs were once used in the production of refrigerants, but are in the process of being discontinued under the UN's 1987 Montreal Protocol.

"Limiting future nitrous oxide emissions would enhance the recovery of the ozone layer from its depleted state," researchers wrote.


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