Hopes for a grand deal were dashed in Copenhagen last December, when talks broke down amid recriminations between rich and developing countries who couldn't agree on how to share the burden for deep emissions cuts, and how such cuts should be verified.
Much of the focus is on China and the US, now the world's top two emitters of greenhouse gases. China insists the US and other developed countries should make more dramatic cuts and do more in funding and transferring technology to poorer countries for green energy efforts.
The US wants China and some other developing nations to bear more of the burden for cuts, and wants a mechanism for verifying such cuts – something Beijing has resisted.
And they're closely watching the attitude of China, the world's largest greenhouse-gas emitter, as it hosts the conference for the first time in the 20-year history of United Nations global climate change talks.
Observers say there's no sign either side is prepared to budge much from those positions. From China's point of view, said Greenpeace China's Yang, the US is doing little domestically – climate change legislation is stalled in the US Congress – and isn't offering much at the negotiating table, either.
"China can't get any of the technology or climate finance it wants, so it feels like there's very little the US can offer," she said. "It's one reason why negotiations have really stalled."