The link points to a story about negotiations on a climate change treaty, in which chief U.S. negotiator Harlan L. Watson says:
We believe that it is best to address this complex issue through a range of programs and technology initiatives.This by way of dismissing the existing international treaty and subsequent protocols built upon it.
As an environmental economist why we pollute and you get a simple answer. Polluters pollute common goods. They save themselves a couple bucks by moving toxins elsewhere, either to the future or to someone else's property, or to property that no one (or everyone) owns.
Environmental economists generally see this sort of system as resulting from inadequate or inadequately assigned property rights. No one builds smokestacks in their own neighborhood, no one dumps toxic waste on their own property, and no one overfishes their own pond. We do overfish oceans that are open to all. We do dump toxins in the air and water that belongs to everyone. And it would be bad business not to.
This is called the tragedy of the commons, referring to overuse of common grazing land in olden times.
Countries that commit to reducing greenhouse gas emission may incur higher costs up front. Long term, the costs may balance out, but paying up front means opportunity costs, etc. So no one will take that first step until everyone else does it. International treaties are ways of getting everyone to commit to particular practices that are better for everyone but where cheating would be profitable.
This is why you needed arms limitation treaties, not just unilateral disarmament, and why you need international treaties regulating greenhouse gases, not just national action.
Though that would be nice, too.
“Hot Time in the Old Town Tonight” by Mississippi John Hurt from the album Complete Studio Recordings (1966, 3:33).