It was hotter by a considerable margin than the previous record year, 1997, and means seven of the ten hottest years in a record stretching back to 1860 have been in this decade.
It will give further credence to the belief that global warming, the overheating of the atmosphere by industrial gases such as carbon dioxide from motor vehicles and power-stations, is significantly destabilising the world's climate.
The figures were announced jointly yesterday by the Met Office's Hadley Centre for Climate Prediction and Research in Bracknell, Berkshire, and the Climatic Research Unit of the University of East Anglia in Norwich.
They said that the global mean temperature for 1998 is now expected to be 0.58C above the recent long-term average, which is based on the period 1961 to 1990. Last year, the previous record, was 0.43C above the average.
Although Britain experienced a cool and damp summer, many parts of the world, from the Mediterranean to Central America, experienced intense heatwaves in 1998.
Scientists at the Buenos Aires climate conference in November announced that the year's record sea surface temperatures, up to 2.5C higher than normal, had killed vast swathes of coral in the southern hemisphere.
"The top ten warmest years have all been since 1983," said David Parker, the Hadley head of climate monitoring. "This year has continued the gradual warming trend seen over the past 100 years; global temperatures in the 1990s are almost 0.7C above those at the end of the 19th century."Reuse content