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Some climate skeptics insist on digging up 40-year old figures like this to suggest that the Earth cooled significantly mid-century, and that mid-century warmth might have been similar to today's warming. Lets take a detailed look at their claims: 1/6 
It shouldn't surprise anyone to learn that our collection of historical observational data has grown by orders of magnitude since the 1970s. Back then (proto-) global temp estimates were based on data from a few hundred primarily mid-latitude N. hemisphere land-only stations. 2/6
Today we have tens of thousands of stations all around the world on the land, and millions of ocean temperature measurements available during the mid-century period, allowing us to create a much more accurate estimate of the Earth's temperature. 3/6
Multiple different groups of researchers around the world – including NASA, NOAA, the UK Met Office, and Berkeley Earth – have all put together historical temperature reconstructions that all agree quite well with eachother and with raw (uncorrected) records: 4/6
While all of these show a relatively flat period of temperatures from 1940-1960, none show dramatic declines evident in early northern-hemisphere-focused land records. This is because modest mid-century cooling is only found in the Northern Hemisphere higher-latitude regions: 5/6
These facts have, of course, been explained to folks like Tony Heller time and time again, and their continued reliance on decades-old incomplete data rather than modern datasets is at best willfully obtuse and at worst openly dishonest. 6/6
