Ok, NASA and IPCC I get. GISS is “Godard Institute of Space Studies” at Columbia University, NY.
What is “GHCN”? Writers should not rely on hypertext to excuse themselves of the need to write clearly.
There are 3 main surface temperature data-set that form the basis of all the IPCC’s analysis. The NASA data-set (GISTEMP) is maintained by the Goddard Institute for Space Studies under the direction of Dr James Hansen. The second is maintained by NOAA and is called the GHCN, which stands for the “Global Historical Climate Network”. The third is the one maintained by the University of East Anglia Hadley Center called “HADCRUT3”.
While it may appear that these are independent data-sets, they all are composed of observations from the same weather stations. The differences arise from which weather stations they choose to incorporate into the data-set and just how they massage the raw data to come up with their “corrected” databases.
Recently all three have been shown to have use mysterious correction methodologies which seem to cause a bias towards an artificial warming trend. These “corrections” vary from dropping observations from high altitudes and / or higher latitudes, which drops out most of the colder temps. Other “corrections” include corrections for location which appear to have been applied inconsistently. Another “correction” is to just ignore large areas of existing data such as in Siberia!