Forecast is: it's the warmest for 1200 years

EUROPE - The whole Northern Hemisphere is experiencing a sustained period of warming that is unprecedented in the past millennium.

A study of temperature records - from tree rings, ice cores and old documents - has found that at no time since the 9th century have temperatures been so consistently high.

The study, published in the journal Science, found that the late 20th century has been the warmest period for the Northern Hemisphere since the records began in AD800.

It has even eclipsed the medieval warm period when vines were able to be cultivated in northern Europe and the Norse explorers exploited the ice-free seas to colonise Greenland and the United States.

Timothy Osborn and Keith Briffa, climate scientists from the University of East Anglia in Norwich, analysed temperature records from America, Europe and East Asia.

The medieval warm period extended from 890 to 1170 and was followed by a period of cooling between 1580 and 1850.

"The key conclusion was that the 20th century stands out as having unusually widespread warmth compared with all the natural warming and cooling episodes during the past 1200 years," Osborn said.

The study is the first to look at a variety of temperature records from the entire Northern Hemisphere. "The late 20th century is the only time that all the records consistently showed warmer-than-usual conditions at the same time," Osborn said.

"The most widespread and thus strongest evidence indicative of a significantly warm period occurs during the 20th century, when greenhouse gas concentrations were at their highest during the analysis period."

The Intergovernmental Panel on Climate Change concluded in its last report on global warming that the 1990s was likely to have been the warmest decade for 1000 years. Osborn said the latest study indicates that assessment is correct.

- INDEPENDENT