It's been interesting to observe the many initial media reports on Tuesday's climate change target announcements, characterizing the joint announcements about climate targets as "deals" or "agreement." Then, after the initial media euphoria, much more criticism, both explaining that there wasn't a deal and also that China's commitment may not mean much. (For example, Harvard's Jack Goldsmith sought to de-hype the media reports in the Lawfare blog.)
On the deal issue, a careful reading of the announcement itself indicates that the US and China's pledges were unilateral commitments that were not in themselves formally linked to each other. So, of course not a deal in the formal sense of an agreement or a treaty. On the other hand, a Wall Street Journal article discussing the run-up to the announcement as well as its orchestration leave little doubt that the decision to announce these goals publicly were the result of mutual reliance on the other's public announcement of future action on GHG emissions. And that sense, the announcement represents a "deal," at least to give the public appearance of going forward in cooperation. Either way one looks at it, though, there really was never any question that these pledges are not intended to be enforceable in any way.
Regardless, enthusiasm for the announcements, was still justified in my opinion - this level of engagement and specificity of public pledges by the US and China on climate change and their mutual engagement on the issue is historic and of critical important for the international community.
I do remain puzzled by the broad media assumption that China's pledge will simply come true, in spite of the difficulties China has had in managing and addressing its existing pollution. Not that the 2030 peak emission goal could not be achieved, especially since it is so far out and there is so much time. But I don't think there is real certainty, unless the underlying regulatory system is reformed in the process. Even with the anticipation of further industrial restructuring and macro-economic changes that will seek to change energy usage and supply so as to limit GHG emissions, it is not clear that that will be enough because of ongoing governance, implementation, and accountability difficulties.
But the underlying regulatory and governance challenges that have made it difficult to solve the existing pollution problems also point to an opportunity. If China's existing pollution control laws and accountability mechanisms were to be implemented effectively, including those contained in the recent 2014 Environmental Protection Law Revisions, that could justify much greater optimism about China's GHG emission trajectory.