Here is why they are hiding the rest of the data. The earlier data showed as much pre-1979 cooling as the post-1979 warming.

1520-0493(1978)106<0755:GTVSMA>2.0.CO;2

I combined the two graphs at the same scale below, and put a horizontal red reference line in, which shows that the earth's atmosphere has not warmed at all since the late 1950's