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World's seas rising twice as fast: study

Sea levels around the world are rising twice as fast as they were 150 years ago because of human-induced global warming, US scientists say in a study released on Thursday.

Sea levels are now rising almost 2mm per year, compared to 1mm annually for the last several thousand years, a team of scientists at Rutgers University and other institutions said.

"The main thing that's changed since the 19th century and the beginning of modern observation has been the widespread increase in fossil-fuel use and more greenhouse gases," said Rutgers professor Kenneth Miller, who led the study. "Our record therefore provides a new and reliable baseline to use in addressing global warming."

The findings, based on drilling studies in New Jersey along the Atlantic Coast of the US, are published in the Nov. 25 issue of the weekly US journal Science.

The study claims that ocean levels 100 million years ago and earlier were 150m to 200m lower than previously thought. It also questions whether any of the Earth's warmer areas were ever fully ice-free.

In a separate study published in the same issue, European researchers found that today's atmospheric carbon dioxide is at the highest level in 650,000 years.

Levels of carbon dioxide, the principal gas that drives global warming, are now 27 percent higher than at any point in the last 650,000 years, according to research into Antarctic ice cores published on Thursday.

The evidence comes from the world's deepest ice core, drilled at a site called Dome Concordia (Dome C) in East Antarctica by European scientists who battled blizzards and an average year-round temperature of minus 54oC and made a 1,000km trek to bring up supplies.

The core, extracted using a 10cm-wide drill bit in 3m sections, brought up ice that was deposited by snows up to 650,000 years ago, as determined by estimated layers of annual snowfall.

Analysis of carbon dioxide trapped in tiny bubbles in the ancient ice showed that at no point during this time frame did levels get anywhere close to today's CO2 concentrations of around 380 parts per million.

Today's rising CO2 concentrations are 27 percent higher than at the highest level seen over the 650,000-year time scale, according to the study, which also appears in Science.

The Dome C core, extracted by the 10-country European Project for Ice Coring in Antarctica (EPICA), outstrips by 210,000 years the previous record-holder, drilled at an Antarctic site called Vostok.

In the past five years, the average global temperature has risen by 0.2oC and this year is on course for being the hottest year on record.

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