Regarding global warming, there are several things to consider:
(1) is global warming occurring? don't be fooled, there is not consensus on this. Actual temperature data has only been collected for the past 100 years, so beyond that they have to extrapolate using sea ice, tree rings, etc. Not saying that those methods aren't any good, but when you're dealing with temperature changes of 0.05C, etc. and the certainty of the measurement process is at about the same 0.05C, how certain can you be with your conclusions. Also, since actual temperature measurements have been conducted, multiple "adjustments" have been made. Knowing where, when, and why is important. For example, if you move the thermometer because they're building something there, does the new location get the same amount of sun, etc.? You'll see that the adjustments have all magically made things warmer. There is not consensus that the adjustments that were made were proper. Statistically, the warming that was seen over the past 70 years has NOT been occurring the past 20 years, despite the climate models that predicted continued warming. Are the models wrong? If they predicted continued warming and we're not seeing it, how can you rely on those models. They don't even reflect the weather we know has occurred, how can you rely on that model going forward to predict what will happen in the future?
(2) If global warming is occurring, is it a bad thing? There is not consensus on that. Many think it's a bad thing... the polar ice caps melt, the oceans rise, Manhattan underwater, the warming apocalypse. Some think it will be a good thing, as crop yields increase with small increases in temperature, etc.
(3) If global warming is occurring, can we do anything about it? Again, no consensus on that. Some believe it is occurring, but the contributions of warming due to man's activities (burning of fossil fuels) is swamped by natural factors that we cannot control (volcanic eruptions, etc.). So some people think that global warming is happening, but we can't really do anything about it, from a statistically significant point of view. One famous environmentalist believes global warming is occurring, but the costs of doing anything about it are so great that money is better spent on other things that will have a much greater impact on the world's citizens. (I'm talking things like cleaning drinking water in the third world, etc.)
(4) Politics: sadly, you can't avoid politics on this issue. Environmentalists have made this their religion. Many are willing to lie, misrepresent data, etc. because of their "faith" in global warming. Many just see this as a great issue to scare people into surrendering more of their liberties, and giving the gov't huge powers to further regulate society. After all, what human activity doesn't touch on the environment? And the internationalists see this as the perfect issue to create international regulations that tie nations closer together, and force them to act all in the same way.
