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              • New phase of polar melting

                November 29, 2011
                by Daniele Bargellini

                Polar melting (Copyright Jonathan Hayward)

                According to British Antarctic Survey scientist Dr Dominic Hodgson we are currently in a “new phase of polar deglaciation”.

                Dr Hodgson’s research compared Arctic and Antarctic ice shelf retreat over the last twelve thousand years and found that the last few decades is the only point in that period when ice shelves have retreated simultaneously at both poles.

                Ice shelves are floating bodies of ice, ranging from fifty to several hundreds of metres in thickness, that stick out to sea from continental ice sheets, like the ones covering Greenland and the Antarctic.

                Hodgson’s commentary paper, published ahead of print on the website of US journal Proceeding of the National Academy of Sciences (PNAS), discusses a selection of recent research into ice shelf retreat.

                He raises the interesting point that ice shelf retreat has not happened in both polar regions at the same time, according to the 12,000 year records for both Arctic and Antarctic ice shelves.

                In contrast, the past few decades have seen ice shelf retreat at both poles at the same time.

                Hodgson’s thoughts echo another research paper, written by a Swedish geologist and published earlier this year, which reported that the current warming trend is the first instance over the last twenty thousand years in which both hemispheres have warmed simultaneously.

                The suggestion that because the climate has varied in the past the current warming trend in global average temperature must be natural is often made.

                But noting that something happened before without human influence does not demonstrate that humans are not causing it today.

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