DURBAN, South Africa—China gave a jolt to United Nations-led climate talks by appearing to call for binding emissions cuts, prompting some industrial powers to reconsider their positions at a conference where few had expected real progress.

Meetings that began last week in this steamy port city appeared destined to end as a well-advertised convention of environmental officials and activists swapping strategies on creating new national parks and shutter old coal-fired plants. Then China's comments by China's chief negotiator...