[Miss Marple]

You make a good point about the data. I wonder if they have graphed temperature data collected in small towns only. What about graphing the data simply from state and national parks and forests?

It is just like the tree ring problem. I want to see different sets of data so that I can see how much each set of data skews the final result.

[NittanyLion]

RE: urban warming. Based on what I've read, upper atmospheric satellite measurements don't reflect an increase in temperature. If greenhouse gases were on the rise, this increase should be present. The fact that only ground-based and lower atmospheric temps have increased is likely evidence of warming caused by man-made heat sinks, rather than greenhouse gases.