Global temperatures have risen by 1.36F (0.75C) above the average between 1950 and 1980, according to an analysis by Nasa’s Goddard Institute for Space Studies of readings from 7,200 weather stations. This beats the previous record high in 1998 and continues a general trend of rising temperatures dating back to 1980.

Readings indicate that the Earth is warming more in the northern hemisphere. Only an event such as a huge volcanic eruption would stop this year setting a new record and this trend would lead to temperatures rising by another 1F by 2030, said David Rind, of the institute. His forecasts reopened fierce US debate between scientists who blame global warming on burning fossil fuels and those convinced that the rise is part of a natural cycle.

The Bush Administration rejected the Kyoto Protocol that sets targets for industrialised countries to cut emissions, because it would put the US at a competitive disadvantage with China and India which, as developing nations, were set no Kyoto targets. But President Bush did agree to develop new technologies to curb emissions after signing a statement, part of the G8 agreement brokered by Tony Blair at the Gleneagles summit in July, that: “We know that increased need and use of energy from fossil fuels, and other human activities, contribute in large part to increases in greenhouse gases associated with the warming of our Earth’s surface.”

Mr Rind said that this year’s rise was “really small potatoes compared with what’s to come”. But his belief that this heralded a longer-term rise of an extra 2F to 4F by 2100 was disputed by George Taylor, Oregon’s state climatologist.

He told The Washington Post that the findings were “mighty preliminary”, and said: “I just don’t trust it.”

Other scientists said yesterday that the recent warming could become self-perpetuating. Ted A. Scambos, of the National Snow and Ice Data Centre in Colorado, said that the warming of the Arctic was likely to accelerate as the Arctic ice shrank, because sea absorbs the Sun’s heat but ice reflects it.

Nasa scientists working with the University of Colorado said last month that the Arctic ice cap had shrunk this year by 500,000 square miles from its average 2 million square miles between 1979 and 2000.

William O’Keefe, chief executive of the George C. Marshall Institute, which is sceptical of global warming predictions, said it was not wise to impose new rules on industry when it was unclear whether rising temperatures were man-made.

Times Recommends

• Obama: the world can expect better of America
• Gulp! Mystery killer threatens French oyster
• Secret of Northn Lights key to space safety