The whole global warming issue has been politicized to the point where rational debate is just about impossible. Believe it or not, there are respected researchers on both sides of the issue. It's far from a consensis.

Agree completely with the first and second sentences. As for the third, I would hazard a guess that a majority of people actually researching it hold with the general theory of human-related global warming, but this is just a hunch. I'll let Tom weigh in here with the obligatory "Well of course they do! The dollars would dry up if they said it wasn't happening!".

The facts known for certain is that the Earth has gone through several warming and cooling cycles over the aeons, most of them long before humans even existed.
Most? Try 99.99999% of em ;-)

The understanding of what caused those cycles is pretty weak, and lacking that knowledge, saying that the currently forecast warming trend is the result of human activity instead of natural causes is a bit problematic.

Actually, most of the mechanisms are fairly well known, though the interplay of the various mechanisms - from Milankovich cycles to volcanic outgassings - are open to interpretation.
Personally I doubt the scientific ability to measure changes due to human activity away from a background of natural variation.

At 46, I'm old enough to remember when some of the same people who now predict gloom and doom from global warming were predicting gloom and doom from a coming ice age. Of course, they said that humans were responsible for that, too. I find it rather difficult to consider them as credible sources.

The exact same people or climatologists in general?
It's a bit of specious argument for someone who generally follows science theory don't you think?
Are you saying that our knowledge of the Earth's climate and prediction models has not improved one iota in the last few decades?