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Past decade hottest for 1,300 years in northern hemisphere

(Agencies)
Updated: 2008-09-02 09:38

The past decade was the hottest in the northern hemisphere for at least 1,300 years, scientists have found.

Despite the damp and gloomy summer, with the Met Office saying this has been the dullest August on record, temperatures across the world have been consistently hotter in recent years than at any time since the Dark Ages.

With a lack of widespread climate records from thermometers before the mid 19th century, scientists have generally used data from tree-rings to look at climate change in the distant past.

However, a new study in published in the Proceedings of the National Academy of Science made a more detailed study by adding other natural climate archives such as corals, ice core samples and sediment.

The study using the expanded database of information found the last 10 years were unusually warm compared to the past 1,300 years. This is further back than a previous study in the 1990s which suggested recent temperatures were warmer than they had been for a millennium.

"Some have argued that tree-ring data is unacceptable for this type of study," said Michael Mann, who led the research team at Penn State's Earth System Science Center.

"Now we can eliminate tree rings and still have enough data from other so-called 'proxies' to derive a long-term Northern Hemisphere temperature record."

If climate information from tree-rings is included, the study found the past decade was warmer than at any time in the last 1,700 years.

The results will come as no surprise to meteorologists who have recorded an increase in temperatures in Europe over the last few years with the longest period of hot weather experienced in Britain in 2006. In 2003 a heatwave across much of Europe killed around 35,000 people.

Most scientists agree that the recent warming is as a result of human activity causing an increase in greenhouse gases. However it will be a surprise to many Britons who have experienced a disappointing summer with heavy rainfall and hot spells few and far between.

The Met Office yesterday confirmed August saw the least sunshine since records began in 1929. Phillip Brohan, climate scientist at the Met Office said the global change is not necessarily reflected in different areas of the world.

He said: "In general as the climate warms up we expect warmer weather on average. But whether or not people observe that in their back gardens is another thing."

Mr Mann said conclusions were less definitive for the southern hemisphere and for the globe as a whole because there was sparser data available for the south.

He said: "Conclusions are less definitive for the Southern Hemisphere and globe, which we attribute to larger uncertainties arising from the sparser available proxy data in the Southern Hemisphere." ole, because there was sparser data available for the south."