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The Urban Heat Island of Shanghai, China
Reference
Chen, L., Zhu, W., Zhou, X. and Zhou, Z. 2003. Characteristics of the heat island effect in Shanghai and its possible mechanism. Advances in Atmospheric Sciences 20: 991-1001.

What was done
The authors evaluated several characteristics of the urban heat island of Shanghai, China, including its likely cause, based on analyses of monthly meteorological data from 1961 to 1997 at 16 stations in and around this hub of economic activity that is one of the most flourishing urban areas in all of the country.

What was learned
Defining the urban heat island of Shanghai as the mean annual air temperature difference between urban Longhua and suburban Songjiang, Chen et al. found that its strength increased in essentially linear fashion from 1977 to the end point of their record in 1997 by a full 1C. They also report that in 1995 the Environment Research Center of Peking University determined that the annual heating intensity due to energy consumption arising from human activities was approximately 25 Wm-2 in the urban area of Shanghai and only 0.5 Wm-2 in its suburbs.

What it means
Chen et al. note that "many scientists (e.g., Jones et al., 1990; Peterson et al., 1999) have compared the city temperature with rural temperature, and have suggested that the effect of an urban heat island is one order [of magnitude] less than the global warming of the air temperature." In the present study, however, the status of these two phenomena is totally reversed, as the recent 0.5C/decade intensification of the urban heat island of Shanghai is an order of magnitude greater than the 0.05C/decade global warming of the earth over the past century, which is indicative of the fact that further intensification of even strong urban heat islands cannot be so readily dismissed. Also, Chen et al.'s conclusion that "the main factor causing the intensity of the heat island in Shanghai is associated with the increasing energy consumption due to economic development" goes hand-in-hand with the finding of McKitrick and Michaels (2004) that there is still a socioeconomic-induced warming bias in the temperature data that are used by the IPCC and others as the basis for formulating energy policy. What is more, the study of Zhou et al. (2004) indicates that this bias may be as much as 0.05C/decade in some seasons in certain parts of the world (they studied China in the winter). Hence, it is looking more and more like what is accepted by the IPCC as the true state of global warming over the 20th century, and especially the last two decades of that period, may be quite different from what actually occurred in the pristine natural environment.

References
McKitrick, R. and Michaels, P.J. 2004. A test of corrections for extraneous signals in gridded surface temperature data. Climate Research 26: 159-173.

Zhou, L., Dickinson, R.E., Tian, Y., Fang, J., Li, Q., Kaufmann, R.K., Tucker, C.J. and Myneni, R.B. 2004. Evidence for a significant urbanization effect on climate in China. Proceedings of the National Academy of Sciences USA 101: 9540-9544.


Reviewed 11 August 2004