September 2, 2009

Nitrous oxide now top Earth emission

The National Oceanic and Atmospheric Administration says nitrous oxide has become Earth's largest ozone-depleting substance emitted through human activities.

NOAA scientists said they have, for the first time, evaluated nitrous oxide emissions in terms of their potential impact on Earth's ozone layer. Not only did they find nitrous oxide to be the top ozone-depleting substance, but they said they expect it to remain so throughout the 21st century.

The scientists said nitrous oxide -- also known as laughing gas and occasionally used by physicians and dentists for its anesthetic and analgesic effects -- 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 emissions of nitrous oxide from human activities have eroded the ozone layer and will continue to do so for many decades.

The study by A.R. Ravishankara, J.S. Daniel and Robert Portmann at NOAA's Earth System Research Laboratory appears in the Aug. 27 online edition of the journal Science.