Read up on chemistry
Because I'm not going to spoon feed you all the facts I learned over a number of years at school and five years at university learning the subject. Here is a summary:
Carbon dioxide absorbs infrared radiation that otherwise woudl reflect back into space. This causes heating. Ergo, increasing the amount of CO2 in the atmosphere increases the amount of solar radiation that is absorbed. In the absence of any other factors, this leads to heating of the atmosphere. Politicise it all you like, if you argue with those facts, you are arguing against reality.
And sorry to burst your bubble, but there is a wealth of accurate data that shows (surprise-surprise) that global temperatures have risen over the last couple of centuries. A lot of this is proxy data (e.g. from ice-cores, tree-rings, etc.) and doesn't cover global measurements, so you have to allow for a certain degree of variation.
What it doesn't show (unless you use dubious techniques to cherry-pick your data) is that the world is getting cooler.
It is, however, in the interests of those who make a profit from emitting large amounts of carbon dioxide to dispute the scientific consensus (or conspiracy amongst a very large number of people who have never met if you have your tin-foil hat on straight). Oil and coal companies, to name two examples, are well known for forming lobby groups, and disguising them as 'think-tanks' to 'argue the controversy' about global warming. The same peope can be hired to argue against evolution, and were hired for a number of years to argue on the behalf of tobacco companies that cigarettes do no harm (you can, in fact, find the information relating to this openly on the internet). I, for one, would be a little disinclined to believe what I am told by such people without a VERY large pinch of salt.
Ironically in all of this, the basic priciple of science is to doubt what you are told and to find out for yourself. Because most people do not have the resources to do all possible scientific research themselves, we have a thing called 'peer review', where results of such research are published for all to see, with experimental methods, conclusions, etc. so that they can be repeated by others. This gives a reasonable level of confidence that these results are correct.
Given the results of the scientific process (such as the computer I am currently typing this on), I have a fair amount of confidence in the fact that this system works. Although it does have a few flaws, when it comes down to it, to attack science is to attack rational thought. Sadly, the quality of education is now so poor in this country that people don't seem know what rational thought is, let alone be able to employ it.