Originally Posted by mdatmo
Satellites are much more accurate than that, they are not perfect but they are very good. Granted they only measure radiation (of various frequencies) that then must be converted to a given quantity (be it soil moisture, wind speed, temperature, etc.) which involves some inaccuracies but these are documented and minimized. It is all part of the process of creating remotely sensed observations.
Edit: Flayle, they directly account for sensor locations and environment. All of the datasets in the graph posted here do.
It was just an example. Regardless of their real accuracy, with the sensitivity surrounding man-made climate change, any inaccuracy needs to be eliminated, which satellites have some. From what I understand the only way to get a direct measurement from a satellite is to have 2 satellies measure the bend a beam sent between them as different temperatures will bend a beam at certain angles.