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Urban Heat Islands of North China
Reference
Ren, G., Zhou, Y., Chu, Z., Zhou, J., Zhang, A., Guo, J. and Liu, X. 2008. Urbanization effects on observed surface air temperature trends in north China. Journal of Climate 21: 1333-1348.

What was done
Noting that "a major divergence of views exists in the international climatological community on whether the urbanization effect still remains in the current global and regional average surface air temperature series," the authors employed a dataset obtained from 282 meteorological stations, including all of the ordinary and national basic and reference weather stations of north China, in order to determine the urbanization effect on surface air temperature trends of that part of the country over the period 1961-2000, dividing the stations into the following categories based on city size expressed in millions of people: rural (<0.05), small city (0.01-0.10), medium city (0.10-0.50), large city (0.50-1.00) and metropolis (>1.00).

What was learned
Ren et al. report that mean annual surface air temperature trends for the various station groups of north China over the 1961-2000 period -- in degrees C per decade -- were 0.18 (rural), 0.25 (small city), 0.28 (medium city), 0.34 (large city), 0.26 (metropolis), and 0.29 (national), which makes the urban-induced component of the warming trend equal to 0.07 (small city), 0.10 (medium city), 0.16 (large city), 0.08 (metropolis), and 0.11 (national), all of which results are significant at the 0.01 level.

What it means
The seven Chinese researchers say it is "obvious that, in the current regional average surface temperature series in north China, or probably in the country as a whole, there still remain large effects from urban warming," noting that "the contribution of urban warming to total annual mean surface air temperature change as estimated with the national basic/reference dataset reaches 37.9%."

Clearly, a huge part of the past half-century's global warming, which climate alarmists attribute to the greenhouse effect of CO2 and methane, is nothing more than the good old urban heat island effect, which is not properly removed from the databases of China and probably many other counties as well.

Reviewed 14 May 2008