I thought we would look at a problem seen between two Indiana towns,Columbus and Seymour. This data is from Dave's favorite site--he seems to have disappeared after I started this sequence of comparisons of data from his preferred data site, showing how abysmal the state of the raw data is in, and this data has been partially corrected. The data is from here
First, lets look at the full record. You can see that the two towns differ in temperature by half a degree a year, first being warmer in one town then the other. These towns, are separated by only 21 miles.
But one can also see that in 1992 and 1993 something strange happened to the temperature. For 2 years it was hotter, almost every day in Columbus. Was Columbus a living hell? Did the devil and his minions bring fire and brimstone to Columbus? No, it is just the normal crap of the raw data. but lest look at it in detail.
The red line is the the running average, a 30 day running average. It varies throughout the 2 years but it is almost always hotter in Columbus. Somebody was doing something to one of those temperature stations to make it hotter or cooler, and they did it for 2 years. No one knows what it was. But this is the quality of data that everyone is basing their hysteria of global warming upon.
Let's look at those 2 years in more detail. Here is the histogram of temperature differences for those two years. You can see it is anything BUT Gaussian,meaning that normal probabilistic statistics won't help it.
It is interesting that we US citizens love to think that we are the most advanced society on earth yet we can't measure temperature better than this.