It’s quite possible that global warming is a man-made measurement artifact.
Here’s a sample:
Here is a well maintained and well sited USHCN station:
Here is a not-so-well maintained or well sited USHCN station:
This site in Marysville, CA has been around for about the same amount of time, but
has been encroached upon by growth in a most serious way by micro-site effects.
The only way surface data can be used with any confidence is to exclude all town/city and airport data – no exceptions. Only rural sites should be used, and by `rural’ is meant strictly `greenfields’ sites where there is no urbanisation of any kind near the instrument. Even when greenfields stations are used, those which are technically supervised (eg. managed by scientists, marine authorities, the military etc.) should be treated with greater credibility than those from sheep stations, post offices and remote motels.
It’ll be interesting to see how many of the US stations pass this sensible test.
A later post will deal with the massaging this data is subjected to after it has been collected from these poorly managed sources.