Systematic biases in temperature measurement may be overstating increases in temperatures

The basic problem of the impact of urbanization on heat measurement is well understood, but the problem may be much worse that previous acknowledged. From Fox News:

The temperature record from stations across the U.S. has been systematically overinflated due to faulty data manipulation and “encroaching urbanity” -- locations near asphalt, air conditioning and airports -- according to a new study. And if correct, it calls into question just how hot our planet is getting.

Global warming believer-turned-skeptic Anthony Watts, a former TV meteorologist, posted a new report online questioning the reliability of weather stations in the U.S. Historical Climatology Network, a 120-year-old weather system that forms one tent pole of climate measurements. As the country has evolved, building urban metropolises and airports and pouring parking lots, the weather stations haven’t moved -- and poorly cited stations are spoiling the data. . . .

That problem of poorly cited stations is well established. A sensor in Marysville, Calif., sits in a parking lot at a fire station next to an air conditioner exhaust and a cell tower. One in Redding, Calif., is housed in a box that also contains a halogen light bulb, which could emit warmth directly onto the gauge. . . .