Despite doubts about the chances of a UN climate deal in Copenhagen next month, some world leaders have launched a new diplomatic effort to lobby for consensus.The UN Secretary General, the Danish Prime Minister and the French President were among those who campaigned for support at a summit of Commonwealth leaders in Trinidad and Tobago. They insist that a deal next month is possible. Ban Ki-moon said: “The momentum for success is growing by the day. An agreement is well within reach.” The Danish PM, Lars Lokke Rasmussen, said: “We sense strong support at the highest level to reach an ambitious deal in Copenhagen. It is therefore my firm belief that Copenhagen is capable of delivering the historic turning point that we all want and that our citizens demand.” Britain’s Queen Elizabeth told the summit the Commonwealth has an opportunity to lead once more. She said the threat to our environment is now a global challenge that will “continue to affect the security and stability of millions for years to come”. New promises this week from China and the US, the world’s biggest emitters of greenhouse gases, have lifted hopes that a deal may be possible.