Copenhagen

Obama's taking quite a bit of heat for the outcome of the recent climate summit. For example George Monbiot writes:

the immediate reason for the failure of the talks can be summarised in two words: Barack Obama

Naomi Klein also holds Obama's feet to the fire.

I think there is some counter-evidence to push back against this notion that Copenhagen was down to Obama's failure to use his powers to fly in the face of special interests and take real leadership on the issue.
In his piece for The Guardian, Mark Lynas argues that in fact the blame lies largely with China.

Wen, he says, was in a strong position because unlike Obama he was not under any domestic pressure to get a deal. Moreover Obama could not agree to anything that would give conservative senators cause to say that Chinese industry was being advantaged. The reason China gutted the deal, Lynas claims, is that its growth is largely dependent on cheap coal; a resource the Chinese will not relinquish without major incentive to do so.

I think there is some evidence to support Lynas' analysis.  The chart below (h/t to James Fallows) shows the number of cloture motions between the late fifties and 2008. Cloture is used to neutralise the threat of a filibuster, which were once used by US political parties as a last-ditch measure to delay votes on bills they opposed but have now come into more frequent use. As you can see from the chart the number of filibuster threats shot up quite dramatically since the Democratic party took control of the senate in 2007.

Broadly speaking, this new rule by supermajority dynamic has dire consequences for the ability of US governments to legislate, and address large scale problems. More specifically, based on my understanding of this data, and the recent health care debate, Obama is limited to measures that would be acceptable to Democratic senators. Agreeing to anything the senate rejected outright would  risk undermining confidence in Obama's ability to represent the (positions and interests) of the U.S. government. The senate rejected the Kyoto protocol 95-0 because of their perception that it required the U.S. to act while letting other emitters off the hook (advantaging their economies to the detriment of the U.S.). With this in mind, it is hard to see how Obama could convince enough senators to allow stronger measures against climate change, unless  (for reasons including those outlined here) the Chinese agreed to robust monitoring of their own targets. The Chinese said "no".

Gregor McDonald strengthens Lynas' case in a presentation available here. It's a little long, so I'll represent the relevant parts of his analysis.

Chinese growth has been powered by coal consumption and as the first chart in this report from the Energy Information Agency shows, coal also tends to be cheaper than other energy sources. Though China has invested in Alternative Energy sources such as wind, building out a robust alternative energy infrastructure is expensive, and the benefits to the transition are only borne out in the long term. Coal on the other hand provides energy quickly. Therefore, it is unrealistic to expect China to commit to absorbing the initial pain of a meaningful transition to Alternative Energy, or cuts in energy consumption that climate targets would require.

It is my perception that an unwillingness to give up cheap coal for expensive Alternative Energy generation techniques is the main factor behind China's recalcitrance. The results of Copenhagen may be far from what most people wanted, but getting developing nations that are major emitters of carbon dioxide to agree that they have a responsibilty to act is a big step that nullifies most potential senate opposition. Even so I doubt we'll see much progress on global measures against climate change until we find a way to make them less unattractive to politicians.