First, absent dramatic progress in reducing greenhouse emissions, it is probably already too late to stop significant additional warming throughout the rest of this century. The changes necessary to achieve those reductions are likely far greater than the world is willing to agree to.
Second, political support for reigning in carbon emissions has been eroding due to a well-financed campaign to create doubt about the existence and causes of global climate change. The campaign has, of course, been championed by the fossil fuel industry, and lately has been heartily embraced by the political right wing. If the U.S.--the biggest energy hog in the world--doesn't commit to significant changes in its ways, why would anyone else?
Third, the economics of fossil fuels are, unfortunately, such as to make it highly unlikely that the world as a whole will rapidly substitute renewable energy sources. Each time the price of oil and other fossil fuels increases, the incentive to find those resources in less accessible parts of the globe grows. As a result, we are not likely to reach a point of "peak oil"--the point at which overall production begins to decline, anytime soon.
Further, if developed nations reach agreements to limit the use of fossil fuels, that will just make them less expensive (because there will be a greater supply) to the less developed world. As long as there is an abundant supply of inexpensive fossil fuels, it is likely that someone will "cheat" on any accord and continue to use them.
Fourth, as the world population grows, and as the middle class portion of that population grows even faster, the new demand for energy grows at a huge rate. We might be able to satisfy the new demand with renewable sources--although we aren't now--but just keeping up is difficult.
That doesn't mean the world shouldn't try. We're in favor of the Copenhagen meetings and an aggressive plan to reduce emissions. And we're still personally committed to reducing our own carbon footprint, if for no other reason than to tell our grandchildren we tried.
More than likely, however, the world is going to have to get used to the effects of global warming. We doubt they're quite as bad as some alarmists would have us believe (albeit they're trying to effect behavior change, so some alarmism is in order); by the same token, the skeptics who say "no problem" are wrong--there will be significant, adverse changes, many already taking place.
We just hope we don't get so far past the point of no return that the effects really are catastrophic, something we probably wouldn't see until around 2100. Catastrophic would be significant melting of the Greenland and Antarctic ice caps, and attendant other changes.
We suspect that in another 20 years, the skeptics will finally have lost the battle--the trend will be clear, but it may really be too late.
One aside: recently, hackers broke into computers of climate researchers in England and released a large number of emails that skeptics have used to create doubt and confusion about climate science. Based on news reports that other climate researchers have been the subject of computer hacker attempts and outright physical break-ins, there's little doubt that this was part of an orchestrated campaign, probably funded by segments of the fossil fuel industry, to throw mud on the climate science.
Some day, we'll be exposed to the emails from the other side--those seeking to manufacture doubt about the science--and it won't be a pretty sight. It will probably occur in the context of litigation, and perhaps some whistle-blowers, just as it did with the tobacco industry. When that finally happens we'll see who's really manipulating the science--and public opinion.