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The people who blame global warming on CO2 emissions have a lot in common with the people who claim that intelligent design is a "theory". Which is ironic since they politically disagree on almost everything else.

Whenever I get into a discussion on global warming with someone in person, they are almost always, universally, completely devoid of first-hand knowledge on global climate history, other factors that can cause the warming and cooling of the earth.  They often sound, remarkably, like the people who come to my door trying to "save" me.  They refer to various unnamed "scientists" and "experts" who have told them what to think and therefore believe it. 

I can be talked into believing that the Earth's temperature has risen in the past several decades. But I am not convinced that it has anything to do with CO2 emissions.  There's very little evidence that the earth's atmosphere has warmed any measurable amount globally.  But surface temperatures are a different thing.  Urban sprawl and humans covering increasing percentages of the earth's surface with cement and other heat-sink materials could certainly create local increases in temperature.  Go into a city in the summer and you can definitely feel it. 

Incidentally, I'm not arguing that human habitation of the surface is causing global warming either.  I am saying that there may be other explanations to it -- if it's happening.  We are, btw, in an inter-glacial period.  That is, we are actually currently in an ice age. The earth is currently cooler than it has typically been when looking at the earth historically over the past 100 million years.

We simply don't know very much on global climate yet.  That doesn't mean we shouldn't try to decrease our impact on the environment. We should try to cut down all our impacts whether that be CO2 emissions, sulfur emissions, CFCs, etc.  But we shouldn't do it because of global warming.  We should do it because we simply don't know what impact it will have on the environment.