Global Warming Validation

I've been reading a good deal about global warming recently, ranging all over the map of ideologies and scientific disciplines. What I've come to recognize is that a significant number of media types, governmental functionaries, and non-climatologist scientists have declared that the debate over global warming is over while the actual scientists who study this sort of stuff remain much more divided on the matter.
When the dust settles, we'll know which side had it right, but I'd really like to know before then. You see, if we decide that global warming is real--and if we turn out to be wrong--then we'll pour a huge amount of money into fighting it. If global warming turns out to be simply an Al Gore hallucination, that money will be largely wasted. And if it winds up being real but not fixable, then we might as well invest in bigger air conditioners.
On the other hand, if we opt to reject the current consensus on global warming then we all fry, drown, or otherwise die. I don't want to be wrong on this one, and since meteorologists seem to struggle to forecast tomorrow's weather, I can't get real excited about their prognostications regarding twenty years out.
So here's the question that I'd drop in the lap of the debaters: What results in what time frame can we agree on to demonstrate who is right? Let me explain. I recall somewhere back in my science education that Einstein theorized about light being affected by gravity. Most physicists accepted this theory as correct as they embraced relativity, but they still performed an experiment. During an eclipse, they noted, the light from a star, traveling past the eclipsed sun, should be bent slightly therefore making the star appear to be in a different spot in the sky. They performed their measurements and waited for the eclipse to see if, indeed, the star's light bent. And it did. Einstein's theory was vindicated.
Today, at my house, the temperature is a balmy twelve degrees, hardly the stuff of global warming. However, I'm not so naive as to believe that one cold day disproves an overall warming trend. But 2007 was not warmer than 2006, which in turn was not warmer than 2005. Presumably, global warming should produce some . . . warming, right? But again, we don't need to see each year inexorably warmer than the one before. But what sort of warming trend should we be able to observe to know that the earth is indeed heating up? Will a five-year trend suffice? A ten-year trend?
I'd like to hear both sides of this debate set out figures that say, essentially, "If we don't observe at least this sort of movement, then we'll shut up and concede defeat." I think they owe us this much. After all, if the Gore crowd is wrong, we're going to flush a lot of money down the toilet, while if the denier crowd is wrong, oodles of people will die. It seems like some level of accountability is the least they could offer.