Leading article: Let us not doom Cancun to failure before it even begins

Snowfalls grip swathes of Britain. Temperatures in Wales dip to minus-17. As Britain shivers in the kind of freezing winter that we normally associate with Eastern Europe, it's hard to remember that the world is at the tail end of the hottest, or second hottest, year on record. That is the problem with global warming. The steady rise in temperatures is incremental and often almost undetectable, especially in the cold northern hemisphere, where some feel tempted to celebrate the prospect of more Mediterranean-style summers.

Unfortunately, the price that the rest of the world stands to pay for more agreeable northern summers is catastrophic in terms of rising sea levels, drought and desertification, which is why progress on curbing greenhouse gas emissions at this week's climate conference in Cancun, Mexico, is vital.

After the failure of the Copenhagen summit last December, expectations couldn't be lower of a globally binding concordat aimed at keeping the rise in temperatures within an environmentally acceptable limit of 2C.

The core problem is that the opposing positions of the developed bloc, led by the US and Europe, and the developing bloc, led by India and China, have not budged much since the Danish summit. The emerging giants in the east still do not want to sacrifice high growth rates to address a phenomenon that the rich industrialised West caused in the first place. The West argues that nothing can be achieved in terms of slowing global warming unless China, or India, come on board.

To compound the gloom, resolve is faltering on the part of the most important Western player. When Barack Obama took office, he pledged that the United States would cut carbon emissions by 17 per cent. But the promise was conditional on Congress giving assent – and that hope looks dead in the water following the Republican gains in the US midterm elections.

No wonder so many world leaders, starting with President Obama and David Cameron, are staying away from Cancun, unwilling to be associated with the possibility of failure, while those attending the talks, like the Environment Secretary, Chris Huhne, are setting the bar as low as possible.

After what happened at Copenhagen, Mr Huhne's caution is understandable. But while the prospect of a legally binding global deal on cutting emissions looks far away, we should we wary of writing off Cancun as "Cancan't". There are areas of possible agreement on side issues, such as finance and forestry. Looking further towards the future, options other than a legally binding global agreement also deserve exploring.

One path ahead leads in the direction of a "coalition of the willing" whose example inspires the rest. The Prime Minister, David Cameron, hinted that he favoured this approach recently, when he urged environmentally conscious countries "to show that green growth makes sense". The bleaker alternative is to abandon any attempt to get all the players to agree to emissions targets and concentrate on mitigating the worst effects of climate change. Britain's chief scientist, John Beddington, appeared to place himself in this camp at the weekend when he said he did not expect a comprehensive agreement at Cancun and believed it unwise "to think that the 2C goal will happen".

That is a depressing thought. But many developing countries are just as worried as is Europe by the prospect of rising temperatures. And while China remains averse to legally binding treaties, it is far more aware of what is at stake in the climate debate than it was a few years ago. We may not see a breakthrough in Cancun but we could see signs of convergence. It's not enough, but it's reason not to give up hope.