The allegations made in today’s Guardian create a misleading picture and require important clarifications in three areas:
1. The FOI request was responded to in full
The FOI request from Douglas Keenan was responded to by the university in full in 2007. The data used in the 1990 paper were indeed sent to Mr Keenan, including both the locations of the stations and the station temperature data for China, Australia and western parts of the former Soviet Union. For China, the data covered the period 1954 to 1983. The data were also uploaded onto the Climatic Research Unit (CRU) website.
2. The accuracy of the data and results was confirmed in a later paper
Prof Jones embarked on a study in 2007 which was published in the Journal of Geophysical Research in 2008. In this later study, CRU researchers worked with a Chinese colleague (Dr Q. Li) from the China Meteorological Administration (CMA) in Beijing. Dr Li had been assessing the consistency of 728 Chinese temperature series and his work was published in China in 2007. This improved CMA data was adjusted to account for changes in location of stations.
CRU requested this improved CMA data for the stations that had been used in the 1990 study, and they were incorporated into the 2008 paper.
Figure 6 from this study (see below) shows the comparisons (as anomalies from the 1954-1983 period) between the averages of the 42 rural and 42 urban sites used in 1990 compared with averages from the same stations from the CMA network. The dashed lines are the averages for the rural and urban sites in eastern China from the 1990 paper. The solid lines are the averages from the same stations from the CMA network. It is clear from the graph that the trends of the CMA data for both the rural and urban networks agree almost exactly with the results from the 1990 paper.
The 2008 study undertook additional analyses using more extensive data and did conclude that there was a likely urbanization trend in China of 0.1 degrees Celsius per decade for the period 1951-2004. But allowing for this, there was still a large-scale climatic warming of 0.15 degrees C per decade over the period 1951-2004 and 0.47 degrees C per decade over the period 1981-2004. The paper concluded that much of the urbanization trend was likely due to the rapid economic development in China since the 1980s, after the period analysed in the 1990 paper.
3. The CRU findings were corroborated by other papers used by the IPCC
The 1990 paper was only one of a number of papers referred to in the 2007 IPCC Report examining possible urbanizations effects.
Jones, P.D., Groisman, P.Ya., Coughlan, M., Plummer, N., Wang, W-C. and Karl, T.R., 1990: Assessment of urbanization effects in time series of surface air temperature over land. Nature 347, 169-172.
Jones, P.D., Lister, D.H. and Li, Q., 2008: Urbanization effects in large-scale temperature records, with an emphasis on China. J. Geophys. Res. 113, D16122, doi:10.1029/2008/JD009916.
Li Q. and W. Li, 2007: Development of the gridded historic temperature dataset over China during recent half century, Acta Meteroloigca Sinica, 65, 293-299 (In Chinese).