Culprit

What links the following: devastating tornadoes in Sussex, the worst floods in England for more; than half a century; and the highest global temperatures since records began?

The British government, at least, seems in little doubt. John Prescott, the deputy prime minister, told the House of Commons the devastating weather of the past few weeks is a "wake-up call to everyone" over global warming.

It is a wake up call that many environmentalists insist is long overdue. Since the late 1980s, they have been claiming everything from melting glaciers in Iceland (under the ice volcano eruption) to vanishing coral in the Caribbean and Indian Ocean points to the same awful conclusion: that the Earth is over-heating - and it's all our fault On the face of it, such suspicions seem well-founded.

But no sooner had Prime Minister Tony Blair added his suspicions, however, than climate scientists were warning of the dangers of seeing patterns in the British climate that don't exist

Researchers from the universities of Newcastle and Exeter unveiled a record of British rainfall dating back to the Norman Conquest It showed the bizarre weather of the past few years is entirely consistent with the natural variations in the climate that have taken place over the past 1,000 years.

Environmentalists argue events in Britain are only part of the picture, and point to recent storms in Taiwan, floods in Bangladesh and fires in the United States as further evidence for global warming.

Even so, the scientific consensus - as expressed recently by the UN Inter-governmental Panel on Climate Change (IPCC) - is that the world's weather has not become significantly more extreme during the past 100 years.

What most scientists do accept is that the Earth is warming up: temperature records from around the world point to the 1990S as being by far the hottest decade of the century. Many scientists also insist the chief cause of this warming is the rising level of carbon dioxide (C02) in the atmosphere, generated by burning fossil fuels such as coal and gasoline.

A decade ago, it all seemed simple. Compel industry to clean up its act clamp down on filthy fossil fuels and gas-guzzling cars and the Earth would be saved, said activists and scientists alike. During the past five years, however, climate experts have found that all the "filth" that industry puts into the air along with C02.actually combats global warming by reflecting the sun's heat back into space.

While the precise effect of these so called aerosols on global warming is still hotly debated, some climate experts think it might even cancel out the warming effect caused by greenhouse gases.

If true, this would have profound implications for those trying to decide how to combat global warming. Demanding a major clean-up from industry might actually accelerate global warming, with who knows what consequences.

It is a possibility that has prompted one leading climate researcher to call for a shift away from controls on C02 and towards controls on methane, a potent greenhouse gas generated largely in the wetlands and rice paddies of developing nations.

While the arguments continue over who is to blame and who should pay, some scientists question the very notion that humans are even responsible for global warming. Instead, they point the finger of blame at the most obvious potential culprit: the sun.

Attempts to implicate the sun have repeatedly been howled down by climate experts, but refuse to go away. Earlier this year, a meeting of space scientists sponsored by the European Union was told of a striking correlation between the temperature of the Earth and the strength of the sun's magnetic field. The correlation stretches back more than a century; and suggests half of the global warming might have been caused by the sun.