I wouldn't say that the UN has ignored the issue. I think they have been pretty clear. Global Warming/Climate change are real, are human induced, and will have serious impacts if not addressed (scientists tend to be non-dramatic, so they say things like "serious" when they mean cataclysmic).
The global community is essentially in a standoff. No one wants to be the first to drop their guard. Behaving that way, whilst being faced with a disaster, is the action of children. And we are going to pay for it. If we were adults we would use what wiggle room we have left to usher in the technologies of the future.
As for our government, well, you should direct your inquiry to Exxon, GM, Lockheed Martin, etc. since they have bought and paid for the politic puppets currently in place. Fossil Fuel companies have trillions of dollars of product in the pipeline. They aren't just going to give that up. Without the political leadership to force them to, we are screwed.