There was disappointment at what has been seen as limited progress made at the UN climate change conference after a fortnight of discussion in Warsaw, Poland.

European Climate Commissioner Connie Hedegaard says the process needs to provide a “substantial answer” to global warming within two years to remain relevant, and there is concern that the UN has lost its credibility as a forum in resolving the issue of reducing carbon emissions.

Hedegaard told Associated Press that the UN might have to consider changing its approach, saying, “Maybe it would be time now to think if there should be themes for the conferences so that not each conference is about everything.”

The two-week session that ended Saturday in Warsaw nearly collapsed before agreements were watered down to a point where no country was promising anything concrete.

Eventually, negotiators emerged with a vague road map on how to prepare for a global climate pact that is scheduled for adoption in two years — work Hedegaard said will be crucial in answering whether the world still needs the U.N. process.

“I think that it has to deliver a substantial answer to climate change in 2015,” she said. “If it fails to do so, then I think this critical question will be asked by many more.”

Governments appear to be more successful in negotiating deals on low-carbon solutions and energy efficiency, outside of the UN framework.

For example, China and the U.S. — the world’s two biggest carbon polluters — this year agreed to work jointly on energy efficiency, carbon capture technology and other mitigation projects.

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