Internationally, inter-imperial rivalry over diminishing resources in the context of a global economic recession has sharpened, as countries fight to maintain or extend the power of their own national set of corporations in hostile competition with all the others.
The Copenhagen conference could more aptly be described as a confrontation rather than a conference, as countries faced off across the diplomatic table. In the end, any possibility of an agreement was torpedoed by an unholy alliance of five heavy fossil-fuel users and carbon emitters led by the U.S. and including China, India, Brazil and South Africa.
This time around, in Cancún, the big governments reason that there's no need to turn up because a deal on climate is so unlikely due to the depressed global economic situation and an incipient trade war. Showing up to a failing conference would just be bad PR. Forced austerity, not clean energy, is what's on the table.