FIRST drafts of a report on climate change say that signs of man-made global warming may already be visible.
If this conclusion is agreed by all 300 scientists on the Intergovernmental Panel on Climate Change in its report due in the summer, it will be a significant shift from the panel's view in 1990.
Global warming was then said to be likely, but could not yet be distinguished from natural temperature fluctuations. The changing consensus has emerged on the eve of a meeting of the 120 nations that are members of the world climate treaty in Berlin.
The latest opinion from the Meteorological Office is that global warming could accelerate. The evidence about climate change comes from its Hadley Centre where a huge computer model has reproduced the 0.5OC rise in global average temperatures over the past 130 years.
This match between what has been observed and what the Hadley simulation predicted would happen by now, based on known emissions since the industrial revolution, increases confidence in the scientists' forecast for the next half-century.
They predict that average temperatures will rise by 1OC by the year 2040. According to the simulation, the temperature rise will accelerate to 0.2OC a decade, the fastest since the end of the last ice age, 10,000 years ago. The models also show significant drying in India, Asia, South Africa and north-east Brazil.
The rise has been replicated by a another huge computer at the Max Plank Meteorology Institute in Hamburg. Previous estimates of man-made global warming as a result of known fossil fuel emissions were much higher.
The current model has built into it the fact that pollution from power stations and industry is cooling as well as warming the planet. Sulphate aerosols, as the particles which cause acid rain are known, have suppressed the effects of climate change by reflecting sunlight back into space before it can warm the atmosphere.
If industrial nations tackle the problems of acid rain, as they are committed to do, global warming will speed up. The computer says that without sulphate aerosols, the temperature rise would be 0.3 per cent a decade.
