Many American politicians want US action on climate change to be linked to Chinese commitments and action because, unless China acts to reduce greenhouse gas (GHG) emissions, they rightly assert, global efforts will likely fail. China is now the world's leading emitter of GHGs, exceeding total US emissions, although not per capita. Thus, any effort to significantly reduce global GHG emissions without China would require far greater and more costly reductions from other large emitters, including the US.
What is often ignored is that China is truly a developing country, with many of the problems developing countries face. For one thing, China has approximately 254 million people (according to the World Bank) living on $1.25/day or less. Those people are not likely to be concerned with climate change, or to demand action on climate change from their government. Likewise, the residents of China's more prosperous cities, which still suffer from exceeding high levels of life- and health-threatening domestic pollution. Overall per capita income in China remains far below the level of the US and other industrialized countries. And China has contributed far less so far to the existing stock of GHGs in the atmosphere.
What does this mean for international climate policy? It means that China is highly unlikely to be cajoled into committing to enforceable GHG emissions reductions. Instead, it's going to have to be paid to play (although it should not be paid, a la Russia, in the very currency the international community is trying to reduce - GHG emissions credits). China's going to have to be offered something of value to it in exchange for a credible commitment to reduce its GHG emissions. Patricia McCubbins of the Southern Illinois University School of Law has suggested (here) that China might cooperate in exchange for more international assistance with its severe domestic pollution problems. That's strikes me as highly plausible.
In any case, it is worth noting that China already has undertaken voluntary commitments relating to climate policy. Over the past 10 years, it has certainly cooperated more with the international community on climate policy than has the US. Among other things, China has become a global leader in experimenting with in situ coal gasification and sequestration.
Finally, there is reason to believe that China is awaiting concrete action from the US before making greater commitments of its own on climate change. In effect, it seems that both countries are waiting for the other to take the next step. The good news is that the countries have been holding relatively high-level negotiations on climate policy. There is reason to hope that those negotiations might lead to a better international agreement than the international community ever could have attained by this December in Copenhagen.