Read here. If you're not yet aware of this interesting "scientific" response, global warming scientists will go out of their way to flippantly dismiss the substantial 'Urban Heat Island' (UHI) effect. Why? Well.....because UHI totally overwhelms any measurable impact from CO2 emissions, and, by the way, it undercuts their desired funded-research, which is dependent on the AGW hypothesis. In the case of New York City, the UHI is absolutely huge, which is indeed a human impact, just not the favored CO2-caused impact.
"...the heat island signal, measured as the difference between the urban core and the surrounding rural surface air temperature readings taken at National Weather Service stations, averages ~4°C on summer nights (Kirkpatrick and Shulman, 1987; Gedzelman et al., 2003; Gaffin et al., 2008)," with the greatest temperature differences typically being sustained "between midnight and 0500 Eastern Standard Time (EST; Gaffin et al., 2008)." And on a day that they studied quite intensively (14 August 2002), they report that at 0600 EST, "the city was several degrees warmer than the suburbs, and up to 8°C warmer than rural areas within 100 km of the city."
For another look at UHI, but this time on the left coast, check out this link.
