The coming year is likely to be the hottest since records began, senior meteorologists have told ministers.
A report to the Government by the Meteorological Office's Hadley Centre – the world's leading authority on predicting the climate – concludes that 2003 is likely to be as warm or warmer worldwide than 1998, the hottest year to date, as global warming increasingly takes hold.
Next year is also expected to witness the Kyoto Protocol, the international treaty to combat climate change, coming into effect – and the prediction will increase pressure on governments to act.
The report by two Met Office scientists – Chris Folland and Andrew Colman – is the result of a sophisticated new prediction system developed by the Hadley Centre. It correctly predicted a year ago that 2002 would be the second hottest year ever, after 1998.
The report says that the most important determining factors of worldwide temperatures are global warming, in the long term, and the El Niño weather phenomenon, on a year-by-year timescale.
Dr Folland explained that it was a particularly strong El Niño that made 1998 so warm, raising global temperatures by 0.2 degrees centigrade.
Global warming adds 0.02 degrees centigrade to worldwide average temperatures every year, he adds, and so the five years after 1998 will have raised temperatures in themselves by 0.1 degrees centigrade, making up half the effect of that year's El Niño.
Another weaker El Niño has begun and it is expected to raise temperatures by about 0.1 degrees centigrade in 2003, causing it to equal 1998.
The scientists say: "The best estimate forecast is for a year equal in temperature to the warmest year on record." They add that it could well be even warmer.
The scientists estimate that there is only one chance in five that 2003 will be cooler than 2002. The hottest 15 years on record have all occurred since 1980 and the three warmest have been in the last five years.