The other part of the surprise is that it's common to hear people (see them write) something on the lines of "Of course we're seeing a warming since the 70s; it was cold in the 70s!" Surely someone along the way did their homework and checked out what the global temperatures were?
Fortunately, if we're looking at science, we don't have to assume that other people did their work, or did it correctly. The alternate word for it is, skepticism. Real skeptics don't make those assumptions, they do the work themselves. The fact that it's work also explains why there are a lot of fake skeptics -- it's much easier to pick the answer you like and reject everything else.
So let's apply some real skepticism and ask what was really going on with temperatures in the 1970s.
I'm working from the NCDC global mean temperatures. I'll take the average of each decade they give, and plot that:
That's rather disappointing. The 1970s were the 4th warmest (of 12) decades in that record. Actually a little worse, as you'll notice I don't have the decade starting in 2000 computed. (I downloaded the file in 2009, it's gotten warmer since then). 4th warmest of 13 decades, behind only 1940s, 1980s, 1990s, and 2000s. But -- be a proper skeptic -- compute for yourself the average for January 2000 through December 2009. I got +0.35 for the 1990s.
My disappointment is twofold. First off is that the decade that I remember as being so very cold, wasn't. In my area it was, and even for a good distance away. But the entire US is only about 2% of the globe. The global average could easily be quite different, and turns out that it was. The 1970s were a relatively warm decade.
The second part of my disappointment is that those people calling themselves skeptics are clearly not skeptics. They never computed decadal temperatures, and never looked to see whether the 1970s were particularly cold. Not only were they not cold, but they were warmer than the two decades before them. Real skeptics would not claim that they were cold in talking about climate change.
