According to Lord Christopher Monckton – former science advisor to Margaret Thatcher, there are only 4 earth temperature data sets used in most climate models: 2 earth based and 2 satellite based.
The two earthbased sets are controlled by CRU and NASA - both key participants in the Climategate scandal.
The satellite data sets are callibrated against the earth data sets.
Suddenly, all of that Climate Science is coming down to a very small "controllable" sample of data.
Well there is a lot of other fluff, but there you have it.