Arctic ice reveals last decade was hottest in 2,000 years



The Arctic is now warmer than at any time during the last 2,000 years, according to a major new study.



Temperatures around the North Pole have dramatically increased in the last 50 years - reversing a long-term natural cooling trend, scientists say.



The study, based on an analysis of ice cores, lake sediments and tree rings, provides compelling evidence that greenhouse gases released since the start of the industrial revolution are triggering global warming, the researchers say.

Researchers secure a floating platform in Alaska to take sediment cores. They reported finding yet more proof that global warming was a dangerous reality

Lead author Darrell Kaufman of Northern Arizona University said: 'Scientists have known for a while that the current period of warming was preceded by a long-term cooling trend. But our reconstruction quantifies the cooling with greater certainty than before.'



The research - published in the journal Science - comes from a team of British and American geologists who tracked summer Arctic temperatures to the time of the Romans by studying natural signals in the landscape.

Their reconstruction found that the Arctic got cooler in the summer months between 1AD and 1900, thanks to a natural 'wobble' in the Earth's orbit around the Sun.



A crying face is revealed in a melting ice cap in Norway

The wobble slowly increased the distance between the Earth and the Sun during the Arctic summer, reducing summer temperatures by around 0.2C every thousand years and causing the 'Little Ice Age' that led to freezing winters in the 17th, 18th and 19th centuries.



But during the 20th century, temperatures began to rise dramatically - even though the amount of sunlight reaching the Arctic during the summer was continuing to fall.



The decade between 1999 to 2008 was the warmest in the last 2,000 years, the research found.



The researchers say the Arctic should still be cooling because the Earth is now about 600,000 miles farther away from the Sun than it was in 1BC.



They estimate that by the middle of the century, summer Arctic temperatures were about 0.7C higher than would have been expected if the cooling trend had continued.



Today, temperatures are around 1.4C higher than they should be, the authors say.



Dr David Schneider, from the National Centre for Atmospheric Research in Colorado, said: 'This result is particularly important because the Arctic, perhaps more than any other region on Earth, is facing dramatic impacts from climate change.

'This study provides us with a long-term record that reveals how greenhouse gases from human activities are overwhelming the Arctic's natural climate system.



'Greenhouse gases are overtaking a natural cycle.'



The temperature reconstruction looked at the amount of algae in sediments in Arctic lakes - which reflect the length of the growing season - and the thickness of annually deposited layers of sediment which increase during warmer summers when deposits from glacial melt water increases.

According to Greenpeace, Greenland's ice sheet has more than doubled its contribution to sea-level rise in the last seven years due to a rapid and unpredicted loss of ice

They also looked at records of tree rings. The amount of new growth of a tree each year is strongly linked to the temperature of the growing season.



The Arctic appears to be particularly vulnerable to changes to the Earth's climate.



Previous research has shown that Arctic temperatures rose three times faster during the 20th century than the rest of the Northern Hemisphere.



Some experts have predicted that the Arctic could be free from sea ice in the winter within the next few decades if the temperatures continue to rise.

