Still, while accepting on Saturday the need for a new agreement, the United States retained the flexibility that it had sought at the outset, fending off European attempts to set binding commitments on emission reductions.
If the government commits to build a new runway, it knowingly signs up to breaking its own "legally binding" climate change commitments on emissions reductions and attempts to tackle the defining global threat facing humanity.
Nicholas Stern, chair of the Grantham Research Institute on Climate Change and the Environment, has been equally confident: "The summit has generated, for the first time, commitments on emissions reductions from the world's two largest emitters, China and the US, and they have acted for the first time to produce proposals for action.
They will then trade credits, which they can earn by surpassing their commitments on emissions reductions or by selling emissions "offsets" earned through projects such as reforestation or renewable energy initiatives, on the Chicago Climate Exchange (CCX), when it opens in early 2003.The cuts they will pledge are likely to be modest.
The United States and the European Union wanted a firm deadline set at the conference in Warsaw for each of the 195 countries party to the talks to make commitments on emissions reductions that will be enshrined in a new global climate pact at a meeting in Paris in December 2015.
Greenhouse gas emissions reduction targets for 2020 were proposed by EU that formalized its support for the Copenhagen Accord on climate change and where presented its commitments for emission reduction targets.
But the delegates' failure to secure agreement on emissions reduction commitments in time to prepare a new treaty for the Paris meeting in two years has created doubts that the 21-year-old forum will be able to take the global warming fight forward after 2020.
Some analysts said China might be unwilling to make larger commitments until Congress passed stalled legislation on emissions reduction targets.
"We agreed with the rest of the global community on emissions reduction targets by 2030... our commitment is very substantial – it's to reduce our emissions by 26-28% on a per-capita basis," he said.
