Quote Originally Posted by poker_pup
Was Carl Sagan a scientist? I can't remember, he was so boring I think he was.

He was on a PBS show "Cosmos" in the 80's claiming next ice age from pollution.
Yes and no. He was mainly an astronomer and cosmologist, and he was heavy into popular publications.

A couple important points here

1) Astronomy != climatology. This is an extremely important distinction in science. On every single subject you can find scientists in other fields who disagree with consensus. But that doesn't matter because they're not qualified. If a biologist says stuff that disagrees with physics consensus, the biologist's opinion can be brushed aside as irrelevant and unqualified. In order for the biologist to express an expert opinion on physics he would need to be involved in physics (and thus would be an accredited physicist as well as biologist)

So when you ever hear anybody say anything about a topic, make sure to examine whether or not they're actually qualified to give an opinion. Now, here I am giving an opinion on topics in which I am unqualified (I'm not a professional scientist of any sort), but I'm also not expressing opinion contrary to consensus. And if an actual climatologist showed up and started telling me how I was wrong and backed it up with data and consensus, I would need to shut my mouth

2) Carl Sagan's Cosmos is a 'popular medium' i.e. speaks to the populous, not the experts. Disconnects between what is said in popular mediums and what is found in science journals are commonplace. What anybody says about anything in popular mediums is not necessarily representative of scientific consensus. If Sagan said that pollution was going to cause global cooling then he misspoke, but even then it doesn't matter what he thought because he was never an active climatologist.