Urban areas differ from rural areas in a number of well known ways, but the IPCC summaries maintain that these effects have been effectively removed when they talk about the recent (post 1960) increases in global surface temperature.
Continuing the series on how bad climate models really are, another paper is in the pipeline on the long-standing influence of urban heat effects (UHI) in the surface temperature data. Ross McKitrick reports that between 1/2 and 1/3 of the recent increase in temperature is due to this contamination (Ross’s website here).
The methodology uses the regression coefficients from the socioeconomic variables to estimate the trend distribution after removing the estimated non-climatic biases in the temperature data. On observational data this reduces the mean warming trend by between one-third and one-half, but it does not affect the mean surface trend in the model-generated data. Again this is
consistent with the view that the observations contain a spatial contamination pattern not present in, or predicted by, the climate models.
Note that this rather gross bias is not present in or predicted by the climate models, meaning the climate models do not have the physical mechanisms to model it. One consequence is that if the models are to fit the recent increase in temperature, some other (incorrect) mechanism must be used (such as H2O feedback perhaps – I don’t know).
Ross has written up the backstory of the all too common obstacles to publication of articles questioning the IPCC here:
In the aftermath of Climategate a lot of scientists working on global warming-related topics are upset that their field has apparently lost credibility with the public. The public seems to believe that climatology is beset with cliquish gatekeeping, wagon-circling, biased peer-review, faulty data and statistical incompetence. In response to these perceptions, some scientists are casting around, in op-eds and weblogs, for ideas on how to hit back at their critics. I would like to suggest that the climate science community consider instead whether the public might actually have a point.