CO2 Science links to this study. Climate catastrophists bend over backwards to try to argue that there are no such thing as urban heat islands. But of course, whenever anyone gathers actual data rather than trying to use goofy computer model approaches, the answer is always the same:
To assess the validity of this assumption, LaDochy et al. "use temperature trends in California climate records over the last 50 years [1950-2000] to measure the extent of warming in the various sub-regions of the state." Then, "by looking at human-induced changes to the landscape, [they] attempt to evaluate the importance of these changes with regard to temperature trends, and determine their significance in comparison to those caused by changes in atmospheric composition," such as atmospheric CO2 concentration….
The three researchers found that "most regions showed a stronger increase in minimum temperatures than with mean and maximum temperatures," and that "areas of intensive urbanization showed the largest positive trends, while rural, non-agricultural regions showed the least warming." In fact, they report that the Northeast Interior Basins of the state actually experienced cooling. Large urban sites, on the other hand, exhibited rates of warming "over twice those for the state, for the mean maximum temperatures, and over five times the state’s mean rate for the minimum temperature."
I would have thought the following conclusion would have been a blinding glimpse of the obvious, but I guess it still needs to be said over and over:
LaDochy et al. write that "if we assume that global warming affects all regions of the state, then the small increases seen in rural stations can be an estimate of this general warming pattern over land," which implies that "larger increases," such as those found in areas of intensive urbanization, "must then be due to local or regional surface changes."