The Goddard Institute for Space Studies (GISS) estimates a quantity they refer to as the Land-Ocean Temperature Index (LOTI), which aggregates temperature measurements from weather stations both on land and at sea, in an effort to estimate the average surface temperature of the earth. This data set contains the annual global LOTI for the years 1880-2018.
YearRaw: The raw LOTILowess: A lowess-smoothed version of the LOTI