The Berkeley Earth Surface Temperature team has reported the results of their first studies of surface temperature records. They have submitted four papers for publication, you can get copies of them here.
Ironically, Anthony Watts has already posted about one of the papers, roundly criticizing their efforts. In a textbook example of “sour grapes,” he complains that they’re making results public before acceptance in a peer-reviewed journal, and about their use of trends over a 60-year period rather than a 30-year period which would match the analysis in Fall et al. Neither objection has any merit. The choice of a 60-year period has only one drawback: it gives Anthony Watts an excuse to whine. The pre-acceptance release is actually rather standard practice in the physics community (that’s one of the things the ArXiv is for).
In my opinion it’s clear what Watts is really upset about — the results from the Berkeley team have confirmed that the other main global temperature estimates (NASA GISS, NOAA/NCDC, and HadCRU) got it right, and that station siting/urban heat island effects are not responsible for any of the observed temperature increase. The real reason all these analyses (including Berkeley’s) show temperature rise is: the globe is warming.
One of their papers addresses the impact of the “urban heat island” (UHI) effect on global temperature estimates. They computed global temperature based on land-based records using all available stations, and that using only stations which they classify as “very rural.” Calculating the trend since 1950 in both data sets, they conclude:
… 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 heat island 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.
The paper includes a graph of their global temperature estimate (based on land stations only), comparing the “all records” result to that using “very rural” stations (the graph shows 12-point moving averages of monthly averages):
I find it interesting that this analysis seems to show even greater warming than reported in Richard Muller’s testimony about preliminary results, and more warming than the GISS analysis based on meteorological stations only (also 12-point moving averages of monthly averages, which I’ve tried to plot on the same y-axis scale):
They also graph the difference between the “all stations” and “very rural” stations averages, which shows that “all stations” actually show less recent warming than indicated using only “very rural” stations. That kind of blows the “global warming is due to UHI” argument right out of the water.
It’s also fascinating to note that the fake skeptics who lauded the Berkeley team when they expected them to contradict the other analyses, have now turned on the Berkeley team like a pack of angry wolves. To the Berkeley team I can only say: welcome to my world.