Temperature highest in 1,300 years

TEMPERATURES in the northern hemisphere have been warmer in the past decade than at any time in the past 1,300 years, researchers said yesterday.

With a lack of widespread climate records from thermometers before the mid 19th century, scientists have to use data from “natural climate archives” such as corals, tree-rings, sediment and ice core samples to work out temperatures in the past.

A new study was published in the Proceedings of the National Academy of Science.

A previous study in the 1990s suggested recent temperatures were warmer than they had been for a millennium.

And if climate information from tree-rings is included, the past decade was warmer than any time in the last 1,700 years — although there are concerns about the reliability of the tree-ring data.

Dr Michael Mann, of Penn State’s Earth System Science Centre, said the researchers had used more sophisticated methods — which allowed them to exclude tree-ring data and still gain a reliable record going back to 700AD.

He said conclusions were less definitive for the southern hemisphere because sparser was data available for the south.