So what happens when you move the sensors? So what happens when the terrain right around the sensors change? The National Weather Service recently concluded a study of two Caribbean ASOS sites. In one case (St. Thomas, US Virgin Islands) the sensor pack itself was moved nearly 1/2 mile. While that may not seem like much, but it "has led to nearly a 20% reduction in the diurnal temperature cycle being recorded at the Cyril E. King Airport since 1998."  Basically this has caused a cooler daytime maximum and a warmer nighttime minimum. In the second case, (San Juan, PR) a new taxiway at the San Juan airport was installed 10 years after the equipment was sited. The new taxiway came within 61 feet of the temperature sensor. While there was no significant increase in daytime maximums, the nighttime minimums increased 1.4ºF.
I have no numbers on how many climate data sites have either been moved or have had significant changes to the surrounding territory, but you have to wonder how much question there now is in the data. I know that the scientists say that they have adjusted for these variances, but when they are dealing with fractions of degrees, how do we know that they are even close to using a correct adjustment?
Bottom line is this. Yes, the climate is changing. However, the climate has always changed. It has never been static. The planet has gone through four major ice ages. We know that the overall temperature was a lot higher during the age of the dinosaurs. Just because the climate has been good for us for this long, doesn't mean that it will always be that way.