Global warming is forecast to set in with a vengeance after 2009, with at least half of the five following years expected to be hotter than 1998, the warmest year on record, scientists reported on Thursday.

To make this kind of prediction, researchers at Britain's Met Office -- which deals with meteorology -- made a computer model that takes into account such natural phenomena as the El Nino pattern in the Pacific Ocean and other fluctuations in ocean circulation and heat content.