Greenhouse gases carbon dioxide and methane are at their highest levels for the past 800,000 years, according to a Swiss-led international research team.
A series of studies published in the Nature journal by Bern University professor Thomas Stocker and his colleagues show that CO2 levels are for example currently 28 per cent higher than at any other time over that period.
"We can firmly say that today's concentrations of carbon dioxide and methane are 28 and 124 percent higher respectively than at any time during the last 800,000 years," said Stocker.
The Bern professor and his colleagues analysed air bubbles trapped in ice cores collected in 2004 as part of the Epica project in Antarctica.
Their latest results come from the final 200 metres of drilling, which ended 3,270 metres below the surface of the icecap. This is the oldest ice ever analysed: previous research had covered the past 650,000 years.
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