@mousy,
Yes GW has been a natural occurence in the past, but what is there to prove that it is now? Maybe a particularly nasty sunspot could be causing it, but is it? I know that all these GHG emissions affect the enviorment negativly even without causing a general warmup, they create holes in the ozone layer, letting in more and more UV rays in, did you know that there are places in Boliva where the inhabitants cannot stay more that 30 minutes exposed to the sun without suffering heavy burns(I will try to find a link since such afirmatives need backing, but it will have to wait till tomorrow)? Not to mention the affects on the biosphere of an industrial zone, even we with all our brains cannot live fully because of these intoxicating emissions, and other industrial waste, how do you think a plant or an animal could have a chance? So what you are saying is based on the past, and everything that is happening could be natural, but we aren't sure it is are we? Even if cleaning up our industries and our domestic emissions does nothing to reverse this warming process, it is only one of the effects that such gases have when released, and as you just said it's not even the most convincing.