Environment: Is the global warming rhetoric just hot air?

The Government's chief scientific adviser has set out the challenges presented by global warming. Charles Arthur, Science Editor, looks at what he has to say while (below right) Nicholas Schoon, Environment Correspondent, asks whether Tony Blair will be able to live up to his green rhetoric.

Slowing and then reversing global warming will initially be a struggle between two groups of developed countries: the "disbelievers", such as the United States, Canada and Australia, and "believers", such as the United Kingdom, allied with the rest of the European Union. Developing countries such as China will join the fray later: which side they join could be crucial to our future.

It may not help, but the "believers" have science on their side. Sir Robert May, the UK government's chief scientific adviser, happens to be Australian, but that does not stop him criticising any country which drags its feet over action to stop global warming.

Sir Robert's 37-paragraph report, commissioned by the Prime Minister in the summer and written in the past couple of months, draws together work by the Intergovernmental Panel on Climate Change (IPCC) and some regional analyses carried out for the UK government last year.

If nobody acts, it shows that there will be an average global temperature rise of between 1.5C and 4.5C - probably 2.5C - by 2050, caused by a doubling of atmospheric carbon dioxide levels. Sea levels will rise by about 50cm (20in) as the warming oceans expand. Weather will become more variable and more extreme. If we act, the report offers various scenarios, depending on the final levels of carbon dioxide. "It's a long, slow process, like turning a ship around," Sir Robert said.

The likely venue for a first, important battle between the two groups of countries is December's meeting of senior government representatives in Kyoto, in central Japan.

Britain will be represented at the conference by John Prescott, the deputy Prime Minister. Certainly, a doughty fighter will be needed in the face of those countries' continued insistence that global warming is either less of a threat than is made out, or that their own growth in carbon- dioxide output - which contributes significantly to the greenhouse effect - can be offset elsewhere, for example by reforestation in the Amazon.

As Tony Blair was speaking at the Labour Party's conference in Brighton yesterday, Sir Robert said: "We will go to Kyoto with the Government's manifesto commitment to reduce the UK's carbon dioxide output by 20 per cent by 2010. The EU is speaking of a 15 per cent reduction. That's a hell of a lot more than [US President Bill] Clinton is offering." He thinks achieving that 20 per cent target will be "difficult - but we have aim for it".

Any commitments made in Kyoto to reductions will be legally binding - possibly with financial penalties for breaking them. Delegates are also exploring the idea of having "permits" allowing a certain amount of carbon- dioxide emission; these could be traded between companies within a country, or even between countries.

Sir Robert hinted that the UK might be prepared to accept a less stringent target if that would persuade other developed countries to reduce their emissions.

But some politicians in the US are suggesting that they could take action abroad - for example, planting forests in developing countries - to compensate for the global effects of their growing greenhouse gas outputs. "I'm like Oscar Wilde on that," said Sir Robert. "Given two temptations, take both. I'd want to see both happen. But of course in politics, I defer to politicians."