It has been my contention for a long time, that rises in recorded temperatures have been polluted by thermometers that are being impacted by quickly growing urban centers. San Antonio is a perfect example...our official thermometer is located on the runway of our international airport. Not only is there a lot of concrete from the runways, but San Antonio International is surrounded by two major highways (Loop 410 and Hwy 281) and large streets, such as Broadway, Wetmore and Bitters.
In a nutshell, rural temperatures have changed very little over the past 100 years.
Below is a link to the study: