Surface - based temperature histories of the globe contain a significant warming bias due to the urban heat island effect. (friendsofscience.org)
I have used it as a baseline for interpreting the global temperature history during the satellite era. (tamino.wordpress.com)
If the goal of the image had been «to portray the most likely temperature history up to the present» there would have been a single curve, not three! (realclimate.org)