At its core, climate change is essentially a collective action problem. The political scientist Stephen Walt has a very fine blog post which lays out why collective action on this issue is so difficult:
In addition to the scientific uncertainties (not about the fact of climate change, but about the impact of different policy responses), dealing with man-made climate change is a classic collective action problem. All countries would like to avoid the consequences of atmospheric warming, but they would also like someone else to pay the costs of addressing it. Furthermore, the worst negative consequences won’t be evenly distributed and won’t occur for several decades, which means that today’s leaders would have to impose costs on their citizens now in order to leave future generations better off. That’s do-able, but hardly a tempting prospect for most politicians. In addition, there is still no consensus on the best way to proceed: some states favor “cap and trade” systems while other prefer a straightforward “carbon tax.” Finally, the main polluters are in very different economic circumstances; the developed world created the problem but now wants to get rising powers like China and India to undertake potentially costly measures that could slow their own growth. Needless to say, that’s not very attractive to Beijing or New Delhi. Toss in the reality that any agreement would be unwieldy, expensive, and rife with verification problems, and you have an issue that makes reforming health care here in the United States look absurdly simple by comparison.