Sense, Nonsense, and Not-Sense

Regardless of whether any of the individual pieces of science hold up (I haven't had a chance to source them), it's actually impossible to prove conclusively that global warming is a result of the actions of mankind and also that it will result in or has resulted in many of the effects (especially the doomydoomdoom ones) in the movie. It's quite simply not how science works.

Right now, the best evidence (and I would argue only evidence) supporting the theory that global warming is caused by CO2 emissions is climate models. In addition to those, we have some hypotheses which are not inconsistent with the existing data.

Why each of the effects that Gore so painstakingly describes in his movie may indeed be happening, in no way could any of those scientists (if they were any good) claim that they were all conclusively the work of global warming. Instead, what Mr Gore did was present a whole bunch of evidence that the world was changing and evidence that the world was warming and very unscientifically (and it could be argued deceitfully) try to strongly imply a connection between the dots. Then he did the scientifically unthinkable, he tried to predict the future. He argued that if the world were to continue warming at some rate, certain extreme consequences will occur. That's not a scientific claim in the least bit as all the connections are conjecture.

No one doubts that over certainly the last 40 years or so that the temperature is increasing, or even that a link between manmade pollution and climate effects is a very compelling theory. However, the danger is equating scientific theory with proven scientific fact. What Shen is arguing (a fair point) is that dealing with global warming in the extreme way that is supported by some of the advocates has some very real economic costs. Not considering those when chasing after a scientific theory (no matter how compelling) is not a very wise move and using scare tactics to make a weak case seem more pressing is downright fraud.