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Ocean Cooling to Briefly Halt Global Warming, Researchers Say

By Jim Efstathiou Jr.

April 30 (Bloomberg) -- Parts of North America and Europe may cool naturally over the next decade, as shifting ocean currents temporarily blunt the global-warming effect caused by mankind, Germany's Leibniz Institute of Marine Sciences said.

Average temperatures in areas such as California and France may drop over the next 10 years, influenced by colder flows in the North Atlantic, said a report today by the institution based in Kiel, Germany. Temperatures worldwide may stabilize in the period.

The study was based on sea-surface temperatures of currents that move heat around the world, and vary from decade to decade. This regional cooling effect may temporarily neutralize the long- term warming phenomenon caused by heat-trapping greenhouse gases building up around the earth, said Richard Wood, a research scientist at the Met Office Hadley Centre, a U.K. provider of environmental and weather-related services.

``Those natural climate variations could be stronger than the global-warming trend over the next 10-year period,'' Wood said in an interview. ``Without knowing that, you might erroneously think there's no global warming going on.''

The Leibniz study, co-written by Noel Keenlyside, a research scientist at the institute, will be published in the May 1 issue of the journal Nature.

``If we don't experience warming over the next 10 years, it doesn't mean that greenhouse-gas warming is not with us,'' Keenlyside said in an interview. ``There can be natural fluctuations that may mask climate change in the short term.''

CO2 Surge

Carbon dioxide, produced mainly from burning fossil fuels such as oil and natural gas, is the chief pollutant blamed for global warming. Since 1988, CO2 levels in the world's skies have increased by 9.8 percent, according to the U.S. National Oceanic and Atmospheric Administration.

Scientists debate how much carbon can be pumped into the atmosphere before the effects of climate change, including droughts, floods and reduced fresh water supplies, become irreversible. For every 1 million molecules in the atmosphere, about 384 are carbon dioxide, according to NOAA.

Global temperatures can't rise by more than 2 degrees Celsius (3.6 Fahrenheit) without risking the worst effects of climate change, according to the European Union. A scenario to stay below that limit suggests that CO2 levels must be stabilized between 350 and to 400 parts per million.

Long-term climate changes in the North Atlantic region affect ``hurricane activity in the Atlantic, and surface temperature and rainfall variations over North America, Europe and northern Africa,'' according to the study.

`Cold Direction'

``Natural variations over the next 10 years might be heading in the cold direction,'' Wood said. ``If you run the model long enough, eventually global warming will win.''

The world will become at least 2.5 degrees Celsius warmer by 2100, compared with the pre-industrial period, Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change, said in March.

``We thought a lot about the way to present this because we don't want it to be turned around in the wrong way,'' Keenlyside said. ``I hope it doesn't become a message of Exxon Mobil and other skeptics.''

Exxon Mobil Corp. spokesman Gantt Walton said managers of U.S. oil company ``take the issue of climate change seriously and the risks warrant action,'' in an interview today.

To contact the reporter on this story: Jim Efstathiou Jr. in New York at jefstathiou@bloomberg.net.