Australian, Korean and US scientists have generated a 65-year record of Southern Hemisphere nitrous oxide measurements establishing a new benchmark against which to compare changes in the long-lived greenhouse gas that is also a major ozone-depleting substance.Published this week in the journal Nature Geoscience, the record is drawn from atmospheric sampling at the Cape Grim Baseline Air Pollution Station, Tasmania, and air extracted from the Antarctic ice sheet
Its significance, says co-author CSIRO's Dr David Etheridge, will be its contribution to the development of emissions protocols as countries step up their monitoring of gases contributing to global warming and ozone depletion.
Nitrous oxide, N2O, is produced naturally by microbial activity in soils and the oceans as well as by agriculture. With a lifetime in the atmosphere of around 120 years, it is eventually broken down by oxidation in the stratosphere.
Scientists have measured a 20% increase in atmospheric nitrous oxide since 1750.
Dr Etheridge said that through analysis of isotopes, which are different forms of the nitrogen and oxygen comprising nitrous oxide, researchers identified that the increase of nitrous oxide was largely from agricultural sources.
"Through these measurements and a close analysis of the record we can also see seasonal cycles in N2O's isotopic composition, as well as large year-to-year variations and long-term trends," he said
He said the unique record of seasonal cycles allows scientists to trace the production and loss of nitrous oxide, from its origins in the ocean and soils to its movement through the stratosphere where it contributes to breaking down ozone.
"Until now the balance between the stratospheric sink and the oceanic source of nitrous oxide has been a key uncertainty in understanding nitrous oxide variations at the Earth's surface.
"This new evidence of the budget nitrous oxide allows
|Contact: Craig Macaulay|