China says it will cut its CO2 emissions 40-45% per unit of gross domestic product by 2020 compared with 2005 levels. It will continue to balloon its total emissions, albeit at a significantly slower clip than if no commitment were made.

“This is a voluntary action taken by the Chinese government based on its own national conditions,” the state council is reported as saying.

China also announced that it will send Prime Minister Wen Jiabao to Copenhagen, less than a day after the US announced President Barack Obama will stop by the negotiations briefly on his way to Norway to claim his Noble Peace Prize.

However, although Wen is viewed as the most knowledgeable and engaged senior-level Chinese official on the issue of climate change, the acknowledgement that President Hu Jintao will not be in Copenhagen was seen as a blow to the negotiations. Hu holds considerably more power than Wen in the Chinese politburo.

Some believe China downgraded its Copenhagen delegation from Hu to Wen as a result of Obama’s decision not to stay for the final and most crucial leg of the negotiations.

The US and China recently signed a clean-energy development pact.

The announcement of China’s “carbon intensity goal” was widely expected, having been hinted at by President Hu since September. Chinese officials say the target will be met through a massive boost in renewable energy, increased energy efficiency, and the adoption of clean-coal technologies if and when they become available.

China has already committed to supplying 15% of its energy needs by renewables by 2020, at which point it is expected to have 100 gigawatts of installed wind capacity.

European officials are thought to be dissatisfied with the 40-45% target, having previously stated that anything less than 50% would not require any structural changes beyond China’s currently running campaign to improve its energy efficiency.

China also announced plans to grow its forest cover by 40 million hectares by 2020, or the equivalent of 60 billion trees.