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Monday, July 6, 2009

Peter Barrett, Tim Naish: Antarctica melting faster than expected

Antarctica melting faster than expected

China Daily, July 4, 2009. WELLINGTON -- Scientists from New Zealand have warned that Antarctica is melting faster than expected.

Recent satellite pictures showed the frozen continent was calving glaciers from its edges at a rate adding up to about 0.4 mm of sea-level rise a year.

That might not sound like much, he said, but the rate of ice loss was increasing quickly -- up 75% since 1996.

The rate of ice loss was up 75% since 1996, and was increasing quickly, Professor Peter Barrett of Victoria University's Antarctic Research Center told the annual Antarctic Conference, held from July 1-3, 2009, in Auckland.

The loss of glaciers at the edges of Antarctic was causing a sea-level rise of 0.4 mm/year, he added.

The global ice loss from Greenland, Antarctica and other glaciers suggested sea levels would rise between 80 cm and 2 m by 2100, Barrett said.

Professor Tim Naish, director of the center, led a team of researchers who drilled deep into the Antarctic rock and discovered ancient records from the last time atmospheric CO2 reached the level it was now approaching.

They found that 3-5 million years ago, seas were warm enough to melt a large chunk of Antarctica's ice when atmospheric CO2 was only slightly higher than today.

Naish said west Antarctica's ice would melt before the larger east Antarctic ice sheet because it sat below sea level and warmed with the ocean.

However, he said the research raised unresolved questions about how much the atmospheric CO2 would need to increase to raise temperatures by 2 °C or more.

CO2 concentration in the atmosphere is now around 387 parts per million (ppm), up from about 280 ppm at the start of the Industrial Revolution.

Modelling by the Intergovernmental Panel on Climate Change predicts temperatures would rise 3 °C if atmospheric CO2 doubled. But the drilling project found temperatures were 3 °C warmer than they are today when CO2 levels were less than 400 ppm, only slightly higher than today.

Dr Barrett said the findings suggested the European Union's target of keeping temperature rise to 2 °C by reining in CO2 to a maximum of 450 ppm might be optimistic.

Modelling suggested CO2 would remain long after humans stopped burning fossil fuels.

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