The latest round of UN climate talks is on a knife-edge between a good outcome and a "car crash", UK Climate Change Secretary Chris Huhne said today.
As the conference in Cancun, Mexico enters its final days, progress needs to be made on the major stumbling block of what is to be done about the existing climate treaty and how major emitters such as the US and China should be included in a future deal.
While there was a good chance of making real progress on areas such as providing finance for poor countries to cope with climate change and tackling deforestation, which creates almost a fifth of global emissions, it would be hard to achieve agreement without overcoming the key obstacles, Mr Huhne said.
Such is the seriousness of the issue that Prime Minister David Cameron has been trying to schedule a call to the Japanese Prime Minister to discuss his country's refusal to sign up to a second phase of the existing climate treaty, the Kyoto protocol.
A failure to get a good outcome at the climate talks would have serious consequences for the climate and efforts to keep temperatures from rising by more than 2C to avoid damaging impacts of extreme climate change, Mr Huhne warned.
"The science on climate change is getting more worrying, not less; the evidence over the last year has got stronger for anthropogenic climate change and we really do have a very limited window to move forward globally to get emissions down."
He warned a poor result could also undermine the UN process, turning the annual climate summits into a "zombie conference" in which increasingly less senior officials attend the meetings and are unable to make any decisions or headway.
"The stakes are extremely high, both for climate change because this is the pre-eminent global problem, and for the existing means of dealing with global problems, which is the UN," he said.
"I do think there's a real chance of making progress, but it's all to play for - this is on a knife edge. We could well have a good outcome but we could also have a car crash."
The talks in Mexico are the latest attempt to make progress towards a new global deal on tackling climate change and come after last year's meeting in Copenhagen failed amid chaotic scenes to secure a new legally-binding treaty on cutting emissions.
It had been expected that the Cancun talks would concentrate on issues where progress could be made, including providing finance for poor countries to cope with climate change and tackling deforestation, but - as in Copenhagen - what happens to Kyoto and the parallel deal that would include other countries has dominated the agenda.
Developing countries do not want to see Kyoto abandoned, as it legally commits rich nations to emissions cuts, but it does not include major emitters such as the US and China, leaving other countries keen to see them involved in a similarly binding deal.
Speaking to journalists after he arrived at the conference hall by bicycle, Mr Huhne said conclusions would not be reached on the issue in Cancun and countries needed to accept a holding agreement, which allows progress on other areas.
"I'm absolutely sure there's a deal to be had and it really does boil down to whether those people who are understandably frustrated at the speed of progress over the last couple of years are prepared to accept an outcome that makes real progress on much of the other dossiers would be getting the show back on the road and injecting a real sense of momentum."
Mr Huhne is chairing talks with other countries today in a bid to make progress on the key issue of Kyoto and a possible new legal treaty.