The CO2 level in the atmosphere is now 372 parts per million. Before the industrial revolution, which began the widespread use of fossil fuels (coal and oil mainly), that number was only 227 parts per million. That's a 30% increase.
CO2 is a green house gas. It is not a pollutant. When you burn something, anything, your best case scenario for non-pollution end result is water and carbon dioxide. There's no magic bullet to solving that as long as are relying on energy sources in which burning them is how we release the stored energy. But pollutant or not, CO2 is a green house gas.
The problem with green house gases is that they trap eat. The suns rays hit the earth and that energy is converted to heat. Much of that heat is returned out into space. But CO2 and other green house gasses keep that heat in place.
The result is that this has probably contributed to the Earth having grown warmer in the past century and it is likely to continue to get warmer. The problem environmentalists face is that they have a very poor track record when it comes to being correct in their predictions of doom. During the 80s there was talk of global cooling. In the 70s there was talk of running out of metals ranging from copper to tin by the year 2000. In the 60s we were told how DDT was going to wipe out all the birds (subsequent research has made the DDT claims look pretty iffy). In short, the environmental movement looks a bit like the boy who cried wolf.
What also hurts is that no one is willing to step up and propose realistic alternative energy sources. If global warming is a serious problem, then serious solutions need to be proposed. Wind and solar power are not serious solutions. At best, they could make up a couple percent of our energy needs today let alone what we'll need in 20 years and that's only if we went crazy with it.
Fuel cells aren't the full answer either because fuel cells only store energy. They're not energy sources. That energy has to come from somewhere. You can't just scoop up some hydrogen and put it into a box. It takes a lot of energy to power hydrogen fuel cells.
As a practical matter, if we want to solve global warming, we have to go with nuclear power. There's simply no other way, any time soon, to provide an energy source that is even remotely adequate. The problem with nuclear power are the waste products. If you think some CO2 is bad, what do you think of nuclear waste?
Unfortunately, there's no political solution to this. The Kyoto accords were a joke. By mid century, China will likely be putting more CO2 in the atmosphere than the rest of the world combined and it would have been excused by the Kyoto accords. India was also excluded along with many other "developing" nations. The Kyoto accords weren't a serious attempt to stop global warming, it was the result of politicians looking for ways to score points with their constituents.
If you accept that we need to bring our CO2 levels under control, then conservation isn't going to do it. Not by a long shot. Once the developing world starts using the same per capita energy as say France, no amount of conservation is going to do the trick. We have to make a fundamental shift from fossil fuels and we have to do that at the same time as we put an end to deforestation. Or we will have to find a technological solution to start removing massive amounts of CO2 from the atmosphere. But I don't see any solutions even remotely on the table at this time that are serious.
They say a frog put into water will let itself be boiled to death if you turn up the heat on it gradually. Hopefully humans are a bit smarter than that. I'm not convinced that global warming is a "bad" thing. And I'm not convinced that CO2 is even a significant cause of it. But I think that there are plenty of other reasons to try to migrate away from fossil fuels.