Koch-backed climate-change denialists have been trying to use the concept of the “urban heat island” — the idea that urban areas are throwing off climate measurements by making it seem warmer overall than it really is — for years now.
They’ll no doubt still try to use it, but they won’t be able to claim that the weight of scientific opinion is on their side. The final nail in the urban-heat-island coffin comes courtesy of Charlotte Wickham, Judith Curry, Don Groom, Robert Jacobsen, Richard Muller, Saul Perlmutter, Robert Rohde, Arthur Rosenfeld, and Jonathan Wurtele (hat tip to Greg Laden):
The effect of urban heating on estimates of global average land surface temperature is studied by applying an urban-rural classification based on MODIS satellite data to the Berkeley Earth temperature dataset compilation of 39,028 sites from 10 different publicly available sources. We compare the distribution of linear temperature trends for these sites to the distribution for a rural subset of 16,132 sites chosen to be distant from all MODIS-identified urban areas. While the trend distributions are broad, with one-third of the stations in the US and worldwide having a negative trend, both distributions show significant warming. Time series of the Earth’s average land temperature are estimated using the Berkeley Earth methodology applied to the full dataset and the rural subset; the difference of these shows a slight negative slope over the period 1950 to 2010, with a slope of -0.19°C ± 0.19 / 100yr (95% confidence), opposite in sign to that expected if the urban heatisland effect was adding anomalous warming to the record. The small size, and its negative sign, supports the key conclusion of prior groups that urban warming does not unduly bias estimates of recent global temperature change.
Res ipsa loquitor.
Mercury Rising 鳯女 