I am no expert on global warming or on geology, but from what I know, I would say that the "global cooling" thing is not technically completely false.
I do not remember the reason given for it by geologists (I'll try to dig up my notes) but according to geological time, the earth right now SHOULD be in a cooling phase.
However, there is no doubt that the average increase temperature of the earth has increased in the last decades at an alarming rate. Way above what would have happened IF we were in a geological phase of warming... which we aren't, according to most geologists!
I know my argument is a bit sketchy right now, because I don't remember all the facts behind it, but I'll see if I can find them back.
But for those of you who insist on seeing global warming as an opinion rather than a fact... think of it this way... what if an "expert" wrote something putting in doubt the idea that feeding drano to your cats will kill them, would you take a chance and leave the drano lying around?
So even if we are not sure that pollution is causing global warming, is that a reason to not do something about it and keep using fossil fuels at an alarming rate? What if there's no global warming and we try to protect the environment from nothing, we'd look like idiots!
(not saying that everyone who doubts global warming is against the environment, but it seems to be the kind of argument of some political leaders