[mkesper]

The real data goes farther back: First link in article is http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.t... going back until 1880 but as averages are compared here you don't need the whole context to compare against.

[sd8f9iu]

And using reconstructions, the data appears to go back even further: https://en.wikipedia.org/wiki/File:2000_Year_Temperature_Com...