I discussed the China network in Jones et al 1990 which is still cited as key evidence against UHI having a material effect on temperature estimates (even in IPCC 4AR). Shortly after Jones et al was published, Wang et al. 1990 ( W-C Wang, Z, Zeng and T. Karl, Urban Heat Islands in China, 1990. GRL 2377-2380, available here – see pages 197-202 ) re-visited what appears to be precisely the same network. Jones et al 1990 reported that they studied 42 Chinese urban-rural pairs. Two authors are in common between the two articles (Karl, W-C Wang). Wang et al say:
“We used 1954-1983 surface temperature from 42 Chinese urban (average population 1.7 million) and rural station pairs (Average population 150,000) to study the urban heat island effects.”
I’ll show their map below, but this seems likely that this is the same network. But the conclusions are quite different.
First, here is a comparison of the two location maps. There is a considerable amount in common, but also differences in details, which may affect Warwick’s proposed identifications.
Left – Location map in Jones et al 1990; right – location map in Wang et al 1990.
As a comparison, I calculated annual averages of 25 HadCRUT3 gridcells corresponding to the grid in Jones et al 1990 (which used 5×10 gridcells and thus overlap but are not precisely the same.) The 1954-1983 values in HAdCRUT3 look somewhat like Figure 2 in Wang et al 1990. However, the amplitude of change in the 1960s appears to be somewhat attenuated.
Left – Figure 2 from Wang et al 1990 showing absolute temperatures; right – average of 25 HAdCRUT3 gridcells (anomalies).
For comparison purposes, here is the 25-gridcell average over the 1850-2006 period covered by HadCRUT3, with the 1953 and 1983 end points marked. There is no trend from 1850 to 1983 – the end of the period included in the Jones et al 1990 study. Wang et al observed that, during the 1953-1983 period, China was impacted by the Great Leap Forward before 1966; the Cultural Revolution afterward, with the Open Door opening only from around 1978. Remarkably, all of the increase in China gridcell temperatures has taken place since the Open Door. Despite increased CO2 in the 20th century, the impact on China appears to have been negligible to 1983.
Wang et al observed:
The differences over the 1954-83 period indicate that since the late 1970s the rate of warming at urban stations is over 0.1 deg C decade relative to more rural stations. … These results suggest that caution must be used when using trends from stations in the vicinity of major metropolitan centers.
Now here’s a really strange quote – given that Wang and Karl were co-authors of Jones et al 1990 –
Our work differs from the recent study by Jones et al 1990. They have shown that any urban bias in their data has been mitigated over eastern China. The reasons for this are not clear.
How can coauthors make a statement like this only 6 months after the original article? It’s seems goofy that they should be arguing with themselves only 6 months later. Jones et al 1990 had concluded that UHI bias in gridded data could be capped at 0.05 deg C (not per decade, per century). IPCC 2001 cited Jones et al 1990 without mentioning Wang et al 1990, as follows:
These results [Peterson et al 1999] confirm the conclusions of Jones et al. (1990) and Easterling et al. (1997) that urban effects on 20th century globally and hemispherically averaged land air temperature time-series do not exceed about 0.05°C over the period 1900 to 1990 (assumed here to represent one standard error in the assessed non-urban trends).
IPCC AR4 again cited Jones et al 1990, without mentioning Wang et al:
Urbanization impacts on global and hemispheric temperature trends (Karl et al., 1988; Jones et al., 1990; Easterling et al., 1997; Peterson, 2003 [which applies Jones et al 1990 in part]; Parker, 2004, 2006) have been found to be small.
W-C Wang, Z, Zeng and T. Karl, Urban Heat Islands in China, 1990. GRL 2377-2380, available here – see pages 197-202 )
Also worth consulting (which I’ll try to review on another occasion is Zhou et al 2004. Liming Zhou Robert E. Dickinson, Yuhong Tian, Jingyun Fang, Qingxiang Li, Robert K. Kaufmann, Compton J. Tucker, and Ranga B. Myneni, Evidence for a significant urbanization effect on climate in China url