The IPCC and NCDC with their GHCN and NASA with their GISS data bases admit the importance of urban warming locally but suggest the effect of urbanization on the global data bases is small and can be neglected. This judgment is largely based on the comments in a paper in 2003 by Petersen that stated: “Contrary to generally accepted wisdom, no statistically significant impact of urbanization could be found in annual temperatures.” This same argument is being used to discard the urban heat island adjustment of the original USHCN data set when the new version 2 is released shortly.

In recent blogs by Stephen McIntyre, Steve discusses Petersen’s paper, his analysis and errors in the analysis and conclusion. Another paper surfaced this week in the Journal of Geophysical Research-Atmospheres by Della-Marta et al., in which the authors blatantly admitted to cherry picking stations and adjusting data (downward) in the early warm part of the record allegedly because of changes in instrumentation. They said this suggested a more alarming warming of 1.6C instead of 1.3C since 1880 in Europe.

See why in this blog and the links provided why both Petersen and Della Marta have it all wrong and why it is the rural areas that become towns, small towns that become bigger towns, towns that become cites where the warming seen is the greatest. Those locations are what cause the global unadjusted data sets to show the warming they do.  That is not to exclude the natural ups and downs due to the natural variability which is superimposed on this urban induced rise. 

Read the full blog and see the many links in WORD here. or for PDF here.