Since 1975, the mean average recorded temperature world wide has increased slightly. Prior to that, it was actually cooling. That is, between 1940 and 1975 the earth was cooling.
Now, it could indeed turn out that the reason temperatures have increased is due to human impact on the environment. CO2 is a greenhouse gas. And we're putting a lot of it in the air. We've significantly increased the amount in the atmosphere since the beginning of the industrial revolusion. What isn't known, however, is how much effect CO2 has on temperature. Anyone who claims they know is lying. It's an unknown and the various computer models basically take an educated guess as to what affect CO2 has on global temperatures. I.e. it's a "fudge factor".
If I were a betting man, I would actually bet that CO2 isn't the cause of the increase in temperature. That doesn't mean I'm against reducing emmissions. I favor reasonable efforts to decrease human impact on the environment (though I am cynical enough to think that left-wing European politicians focus on CO2 in order to deflect from the amount of sulfur, soot, and heavy metals that Europe dumps into the air per capita compared to the US, Canada, and elsewhere). But I am also not in favor of any sort of massive, immediate overhaul to our economy.
Global Warming theory is weak science. The definition of weak science is whether it relies purely on consensus or not as opposed to scientific method. E=MC^2 is fact. It's been proven. Even evolution, which has its share of critics, works on proven scientific principles and has fossil evidence (don't hijack the discussion in the comments area about evolution). Global warming, for instance, isn't even a theory. It's a hypothesis. CO2 is a green house gas. We put a lot of CO2 into the atmosphere. The temperature since 1975 has increased. Therefore, CO2 is the cause. That's it. That is basically the entire argument. And they say it's the cause because there's a "scientific consensus" around it made by many people who have an economic reason to be in favor of it (just as there are those who have an economic incentive to oppose the CO2 hypothesis).
If you've watched films like "An inconvenient truth" note how much time is given over to "proving" the temperature has increased (I don't know anyone who's arguing that it hasn't) and how much damage higher temperatuers would do to the Earth. But how much is actually spent making the case that humans are the cause? Virtually no time. That's because the paragraph above states the entire case. CO2 is a greenhouse gas. We create a lot of it. Temperatures have increased. It's sure a good thing there aren't any other..you know..inputs into our system like a massive fusion powered gas fire fall thousands of times larger than the Earth nearby sending terrajoles of energy into our system...but I digress..
So like I said, if I was a betting man, I would bet that CO2 isn't the cause of the slight global increase in temperatures. I think there are other, much more likely, possibilities such as increased solar activity or slight changes in the orbit of the Earth or tilt of the earth.
I don't claim to be a scientist, but I am pretty good at analysing statistics. And so, if in say 5, 10 years the mean global temperature starts to dip -- i.e. definitively dip like it was doing pre-1975 -- what will the environmentalist movement do? Given the hysteria over global warming, does anyone think for one moment that the environmentalist movement will say "Oops, we're sorry, we really have no idea what we're talking about."? Or, would they simply come up with another "man made" reason that over-compensated for global warming? I think we know the answer.
That's one of the reason I can't take environmentalists seriously. They are so often completely shameless in their claims. They take no responsibility when they're wrong. Heck, they rarely acknowledge when they're wrong. As a result, I'm not inclined to latch onto the latest faith-based chicken little mongering from them. In the meantime, I'll try to live my life as I always have -- with as little impact on the environment as I can do without compromising my standard of living. But I'll also oppose attempts by the irresponsible to cripple our economy and way of life.