Update: The code I used to generate the frames for the animation is now available under the GPL.
The temperature data we have now is not the output of a well-designed measurement process. It could not have been. Throughout time, humans measured and recorded temperatures and weather conditions where they lived and where they traveled.
The GHCN database
has been employed in several international climate assessments, including the Intergovernmental Panel on Climate Change 4th Assessment Report, the Arctic Climate Impact Assessment, and the State of the Climate report published annually by the Bulletin of the American Meteorological Society.
A few years ago, I tried to get an idea of the extent and scope of GHCN data by plotting the temperature series for each individual station.
This time, I decided to not worry about the actual measurements, but just lay out the locations of temperature stations with data in the unadjusted mean file v2.mean.Z every month in the years spanned by the GHCNv2 database.
The result of that effort is the following animation:
Only you can prevent thermometer suicides
From time to time, I and many other more prominent commentators (including, but not limited to, Steve McIntyre, Anthony Watts, E.M. Smith) have noted the disappearance of thermometers from the main temperature data sets.
In case you miss it in the animation, here is what we are talking about: