China, US agree to work together on warming, four years after Copenhagen stand-off

When the world's top two carbon polluters finally sat down on Sunday and signed an agreement on taking joint action on the growing dangers arising from man-made climate change, bitter memories of the 2009 Copenhagen summit still lingered in the minds of some Chinese witnesses of the stand-off between China and the US.

At the United Nations climate talks in Denmark's capital four years ago, China and the United States traded barbs, blaming each other for blocking progress as they disagreed on the fundamental question of how to share the burden of slashing greenhouse gases that cause global warming.

"I bet whoever helped draft the statement was not in Copenhagen," said a former climate negotiator after Foreign Minister Wang Yi and US Secretary of State John Kerry agreed that both sides would dedicate themselves to working together to tackle warming.

In fact, the thinly disguised bilateral hostility extended beyond the negotiating room in Copenhagen, where US President Barack Obama reportedly broke into a meeting between former premier Wen Jiabao and leaders of several emerging economies, and brokered a deal. Another stand-off occurred at a session of the UN talks in Tianjin in 2010, when top US climate envoy Todd Stern blamed China for shirking responsibility, while the host's chief negotiator, Su Wei, hit back, likening Stern to a pig character in a Chinese myth for making unfounded countercharges.

Although the rift between China and the United States remains unresolved, the renewed partnership marks a change of strategy by the two biggest energy consumers in international climate politics, as they may both soon face growing pressure to slash emissions of greenhouse gases.

China is now exempted from any mandatory carbon cuts as a developing nation, and insists it should not submit to such binding reduction targets, as it still needs to grow its economy.