re: #799 iossarian

Well, I’m glad you asked, since I specifically asked him that question the last time we met (we were out for a few beers in a small group that also included an AGW skeptic/denier friend of mine).

He said that the current warming is much, much more rapid than can be explained by the models that are used to explain past ice ages.

So the answer to your question is that no, past warming was not anthropogenic (I think that’s the word you’re looking for) and that yes, current warming is anthropogenic.

The only remaining open questions are around the specifics of the models used to predict just how bad the current situation is getting.

Just to add to that, heating up a planet is hard to do. Planets are big and have a lot of thermal inertia.

There are only so many mechanisms that can pull it off. Orbital variations and volcanic activity are two of the biggest.

Right now, as per orbital variations, we should be cooling (yet we are warming at an alarming rate) and there has been no dramatic volcanic activity of the sort, that could do this, in the past 200 years.

Since it is well established that CO2 is a GHG, and it is easy to directly measure our output of it and concentrations of it in the present atmosphere, we know we are doing it. We are the only viable cause left.