Well, for one, Michael Chriton isn't a fan of the environmental activism or the global warming studies.
Global warming is a reality though. In the past 100 years, the earth, has in general gotten about 1-3 degrees celcius warmer. The question is why? Some belive it to be caused by the greenhouse effect and our pollutants. But that depends on your trust in how we measure CO2, and how good our models of prediction are. Others believe this warming is natural and not caused by man.
It is hard to know where the truth lies because the earth is a dynamic and very complicated system. Don't believe that everything is supposed to stay the same, whichever side of the debate you are on.
edit: linky poo:
http://www.crichton-official.com/speeches/senate.html