Highest temperatures for 1,300 years
Tuesday, 02 Sep 2008 00:34
Northern hemisphere tempertaures warmer during last ten years than any time in past 1,300 years
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Scientists have said that surface temperatures in the northern hemisphere were warmer over the last ten years than any time during the last 1,300 years.
Looking at a wide range of data, including marine and lake sediment cores, ice cores, coral cores and tree rings, the scientists claim to have developed a long-term temperature record proving the record temperatures during the last decade.
"We looked at a much expanded database and our methods are more sophisticated than those used previously," Michael Mann, associate professor of meteorology and geosciences and director of Penn State's Earth System Science Centre, said.
In an article, published in Proceedings of the National Academy of Sciences today, the authors said that the data was not so conclusive for the southern hemisphere but the problems of tree-ring data had been overcome.
The data has been long-term problem for scientists because older trees produce narrower rings and when combing this information with that from younger trees, information regarding long-term temperature trends can be lost.
"Ten years ago, we could not simply eliminate all the tree-ring data from our network because we did not have enough other proxy climate records to piece together a reliable global record," Mr Mann said.
"With the considerably expanded networks of data now available, we can indeed obtain a reliable long-term record without using tree rings."
The scientists conclude that even without the use of tree-ring data it is clear that the anomalous nature of recent warmth, which most scientists believe to be a result of human impacts on climate, is a reality.