There are huge uncertainties to do with the science that goes into the computer models that predict the future

Prof David Unwin, Birkbeck College, London

Meeting in Shanghai, China, the Intergovernmental Panel on Climate Change (IPCC) said the Earth would warm up in the coming 100 years faster than at any time in the last 10,000 years. And they pointed the finger of blame squarely at human activities, in particular fossil-fuel burning.

The panel's Working Group One said computer models were predicting temperature rises of between 1.4 and 5.8 degrees Celsius over the coming century and sea level rises that could be measured in tens of centimetres. It said there was now little doubt about what was happening to the planet's climate and governments should act to curb greenhouse gas emissions.

But several scientists outside the IPCC criticised what they described as the "arrogance" of the UN body, insisting that the evidence for global warming was still far from certain.

Climate uncertainties

Sir John Houghton, the former UK Met Office chief who co-chaired the Shanghai meeting, said that, in his view, there could no longer be any doubt about the human effect on climate.

Some believe indirect solar effects have a bigger impact than the IPCC will concede

"The evidence is certainly sufficiently strong for countries to take action based on what we've said," he told BBC News Online. "I think there are very few scientists who'd disagree with the IPCC. And most of those who do disagree have not published much," he added.

However, the prominent global warming sceptic Professor Philip Stott, from the University of London, was quick to disagree. He said recent research had damaged the credibility of the IPCC and its climate predictions.

"In the last month alone, serious scientific studies have undermined the whole basis of these predictions, with the temperature over the oceans seen as exaggerated by up to 40% and the very relationship between carbon dioxide and temperature questioned."

Political response

He added: "The IPCC models and correlations are not new; they are re-cycled 'old hat'. It is essentially a political response to the collapse of The Hague climate talks."

Professor Stott said computer models presented various "stories" or scenarios and people should not see them as outcomes that were bound to happen.

"There are over 40 such stories; inevitably, of course, the media selects the very worst storyline," he said.

His concerns were echoed by Professor David Unwin, an environmental scientist at Birkbeck College, London. He said the IPCC was guilty of glossing over many of the uncertainties in climate science.

"These uncertainties are never really made explicit," he said. "The IPCC will give you error bars but there are huge uncertainties to do with the science that goes into the computer models that predict the future."

He said the models had progressively drawn back from the real doomsday scenarios of a few years ago as climate processes had become better understood and incorporated into calculations. "And in my view, and in the view of many other scientists, this refinement has a long way to go."

Weather hazards

Professor Unwin said the IPCC, in becoming "fixated on the control of carbon dioxide as a measure to tackle global warming", had allowed other issues such as energy conservation and cleaner air to slip off the agenda.

"And it has made light of all the other levers that society could pull to aid and adapt its way out of the problem that we may or may not have. All the social science evidence on weather hazards shows that, by and large, trying to modify the hazard isn't a strategy that works.

There is a lobby which makes money out of global warming promotion and research, and governments around the world collect taxes on the back of it all

Piers Corbyn, weather forecaster

"I would like the IPCC to stress the steps that society could take to adapt better to the consequences of global warming - and that includes managed retreat from the shoreline, not building on flood plains, care with water conservation and scheduling, and so on."

Piers Corbyn of Weather Action, a company that provides long-term forecasts to UK industry, claimed the IPCC had quite simply got it wrong. Corbyn, like a large group of solar scientists, believes the UN body has underestimated some of the indirect effects of the Sun on the Earth's climate.

"Particles and magnetic effects from the Sun are the decisive influence that controls world temperatures," he said. "The evidence can be seen in the graphic representation of geomagnetic activity plotted alongside world temperatures. The two correlate very closely.

"I think there is a political agenda here. There is a lobby which makes money out of global warming promotion and research, and governments around the world collect taxes on the back of it all. If governments are serious, they should support research into solar effects."