Ocean nitrogen provides limited climate help, says study

Nitrogen entering the world's oceans from human activities provides only limited help in fertilising tiny marine plants that help to slow global warming, Reuters quoted scientists as reporting on Thursday.

"As much as a third of the nitrogen entering the world’s oceans from the atmosphere is man-made," according to a team of 30 scientists writing in the American journal Science. "It’s not as good a thing as some people would like it to be," Peter Liss, of the
University of East Anglia, told Reuters.

In theory, extra nitrogen acts as a fertiliser to spur growth of microscopic plants that absorb carbon dioxide, the main greenhouse gas blamed for global warming. But the study — by researchers in nine countries, including China — said there were unwanted side-effects — including the production of another greenhouse, nitrous oxide, and possible disruption to marine life.

Some scientists argue that artificially pumping nitrogen into the oceans should be eligible for credits as part of United Nations plans to slow global warming beyond 2012. "But you couldn’t get carbon credits for all of it," says Liss. "Two-thirds of the carbon will be released again in the form of nitrous oxide.

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