Love for alternative thories aside, you can't ignore the CO2
What a lot of people are missing, is that even if you find another plausible explanation for the warming, you can't just ignore the CO2.
CO2 is a greenhouse gas. This an absolute, and undisputable scientific fact. (yes, we actually have some of those in science, it is not all models and hypotheses). This we know from looking at the CO2-molecule in particle physics and radiation physics. We can accurately decide the absorption and emmission properties of the molecule, as well as its scattering properties, all as a function of wavelenght. CO2 does interact effectively with infrared light, "heat radiation", of the wavelenghts the Earth emmits. Spectroscopy will tell you the same thing.
Millions of years of data(ice cores, acidity of sediments, erosion rates, fossils ++) tells us that the CO2 levels in the atmosphere has varied between 100PPM (parts per million) in cool periods to 200PPM in warm periodes. It is now 400PPM.
(This is from the big international report released not so long ago. Don't remember it's name at the moment..)
This increase in CO2 is our fault. We know this by measuring the isotope "fingerprint" of the carbon. (you can tell very accurately which coal mine or oil field the fuel was hauled from. In the atmosphere they mix of course, but you can still tell CO2 from breathing, volcanism or industrial use apart very easily)
So: The increased CO2 content in the atmosphere would predict a rise in global temperatures. And lo and behold! - there it is! The global temperatures have increased, with roughly the same rate as the CO2 content would predict. ("roughly" because of lags, and various feedback mechanisms, both positive and negative)
2 + 2 = 4
We are having a global warming, and it is our fault.
Ah, you say, but what about
2 + 2 - 2 + 2 =4?
What if there is another effect, which cancels out the effect of the CO2, and then the actual increase in temperatures are coming from something else, a natural effect of some sort, say solar activity? Can you boffins absolutely exclude that possibility?
No. But they are working on it. As we get more evidence, we are able to better estimate the "fit" of the two models. The current status is that there is a 90% confidence for the 2+2=4 model, which should be sufficient. (absolute proof in an empiric science comes only after the fact, and will then be irrelevant)
So for all of you that want to believe in the alternative theories(and if you do choose to believe the 2+2-2+2=4 verion it is not because evidence nor logic supports it, because you want to verrry, verry much..), just finding another "heat source", (be that increase in solar radiation, variations in cosmic radiation, increased dynamic friction against the interstellar medium, variations in the Earths albedo, or aliens with a huge microwave beam pointing our way) is not enough. You can't just ignore the CO2. It is there, and it is heating us up. Regardless of you heat source of choice, you must also find a cancelling effect!
PS. Computer models, unreliable as they are, are not used to predict/prove global warming, or the effects of CO2. Those are given. The models are only used to predict the RESULTS of global warming on climate and weather patterns in the time to come. These might be wrong, and are frequently disputed, but those disputes does not call in to question the solidity of the CO2->global warming theory. The media, and most people, doesn't seem to differentiate these things very well.