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Ice coring

British Antarctic Survey scientist with a newly drilled ice core.

How Antarctic ice cores give us clues about Earth's future climate

26 January 2009

Science writer and broadcaster Richard Hollingham meets Dr Robert Mulvaney at the British Antarctic Survey, who explains how collecting ice cores from all over Antarctica gives scientists a unique window into the Earth's past climate.

Ice cores collected from thousands of metres beneath the Antarctic ice cap contain tiny bubbles of air trapped when snow fell on the continent hundreds of thousands of years ago. By extracting the bubbles, scientists can measure the levels of carbon dioxide and methane in the atmosphere as far back as three quarters of a million years ago.

Throughout this time, they have found temperature has followed carbon dioxide closely. As carbon dioxide levels rose, so did temperature.

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Crucially, levels of carbon dioxide in the atmosphere today are higher than they've ever been during an interglacial - a period of time between ice ages, which is what we're in now.

The ice cores tell us that the amount of carbon dioxide in the atmosphere today is unusual, and almost certainly down to man-made carbon dioxide emissions.


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Your comments

Historical CO2 record from the Law Dome by D M Etheridge et Al;
Although the temperature in the ice from the medieval warm period follows that as described in documents from that period no such variations in carbon dioxide levels are found in the ice cores, which there should be, as when the temperature increases so carbon dioxide is released from the oceans and from thawing tundra. If the water it is not fully saturated with carbon dioxide when the snow fell any carbon dioxide in the atmosphere at that time will, with time and the increasing pressure, diffuse into the ice until the level of carbon dioxide is the same in both the ice and trapped air. It is only if the ice is saturated or if there has been insufficient time for the levels to equalise that the carbon dioxide in the trapped air will be above the saturation level. It is therefore not possible to say what the levels of carbon dioxide in the atmosphere were during the medieval warm period from the ice cores nor in the previous 640,000 years.

Philip Seager, Rowstock Didcot
Monday, 23 March 2009 - 22:11

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