The March 1, 1975 edition of Science News included the graph below. It showed that Northern Hemisphere temperatures dropped by 0.4 degrees between 1940 and 1970.
The current GISS northern hemisphere graph (1900-present) is shown below. It shows a smaller drop.
The image below shows the 1975 graph (green) overlaid on the GISS graph. Both graphs have the same scale. The 1975 graph is offset by 0.25 degrees.
Note that both graphs agree closely from 1900 to 1940. But GISS shows a much smaller cooling from 1940 to 1970. The latitude bands are not identical, but the missing tropics show less cooling- which would make the discrepancy larger if they were included in the GISS graph.