Several years ago I found an address Isaac Asimov gave to MIT students in the 1970s in which he seems to be endorsing the anthropogenic global cooling hypothesis. One of the points of evidence he gives is that global temperatures had been cooling slightly since the 1940s, and he attributes this to aerosols (smog). As far as I know, this is completely correct! Global warming did have a pause of about 30 years, with a very very slight declining trend, in the middle of the 20th century, and I think modern models attribute that to aerosols. But greenhouse gas emissions eventually powered right through (and some societies managed to reduce aerosol pollution).