The following is submitted without comment on the global warming debate. It is intended as a tool to evaluate the data, not to take a side.

Data Source/Type
Advantages
Problems
Satellite measurements / Global Very accurate, though some correction must be made for cloud cover. Limited Data (<40y)
Ground measurements / Global More than a century of data (although the author is uncertain if this is really long enough to be considered an advantage). Inconsistent siting practices produces noise that reduces the sensitivity of the data. (i.e. in the US a survey of 948 of the 1221 stations found that only 10% of sites met the National Weather Services siting criteria [see surfacestations.org])
Antarctic glacial melting and buildup / Southern Hemispheric Proper ice coring can produce data going back on the order of 100,000 years. Size and distribution of ice sheet makes calculating thermal lag difficult.
Arctic ice cover / Northern Hemispheric Can be estimated from naval observations for almost 400 years. Is almost entirely over water so thermal lag is large (author estimates it yields a three to five year average of northern hemisphere temperatures).
Greenland glacial melting and buildup / Northern Hemispheric

Proper ice coring can produce data going back several thousand years.

Thermal lag is low; yields a nearly real time annual measurement.

Longitudinally biased.

There is some data distortion during ice ages due to surrounding ice on the water.

Karl Barber 3/6/2010
Believe it or not I woke up to this this morning. Feel free to replicate this page.