Michael Crichton interview about Global Warming

http://dailyablution.blogs.com/the_daily_ablution/2007/03/seven_answers_f.html

Despite all the huffing and puffing, the truth is no one knows how much of the current warming trend is caused by man.  Some of it surely is. And some of that anthropogenic warming is caused by the man-made rise in CO2.  But how much is attributable to CO2 is not known.  In the absence of that vital knowledge, people speak of a consensus of scientists. That's a way to get around the lack of knowledge and the inability to predict (which is the conventional proof of scientific knowledge, hence the usual emphasis in science on testable hypotheses.)