...why are these guys doing a literature review instead of looking at the real data, e.g. actual temperatures? If they did, they could not help but see the trend in colder temperatures. There is no reason why there couldn't be a cooling trend in the '60s and '70s that ended abruptly. Tree ring evidence show that on a number of occasions the climate has made sharp changes.
I'd commend the actual paper to the anonymous commenter. If he/she reads it, he/she will see that we did look at the actual data, and discussed it in some detail - both what it showed, and how scientists at the time responded to what they were seeing.
Spammers, don't bother. I delete spam.