The English CRU high resolution grid point material promulgates 20th century China climatic change – each group of 2 ‘–¡Wen Xinyu, Wang Shaowu, Zhu Jinhong – atmospheric sciences, 2006 – scholar.ilib.cn ten thousand sides data resources system Atmospheric sciences CHINESE JOURNAL OF ATMOSPHERIC SCIENCES 2006

The above article says:

They slightly differ from each other in the 1920s, when CRU underestimates the warming change in China, and therefore overestimates the warming trend of the whole century.

I guess these analyses are relevant to why CRU under-estimates Chinese warming in the early part of the century. One would expect that the CRU and Chinese temperature data would have a very high correlation since by and large they begin with the same data. A correlation of 0.84 is not very high under such circumstances and things like these CRU truncations and adjustments may explain why the correlation is not higher.

Abstract:

The operational observations in China started in 1951. The availabity of instrumental observations is poor in the first half of the 20th century. Therefore, it is difficult to use them in discussing long term climate change issue. Although a number of proxy data could be used, the deficiencies are apparent, such as the coarse temporal and spatial resolution, etc. The University of East Anglia recently released the latest version of high resolution grid dataset, named as CRU-TS2.1. It is a completely covered monthly dataset of surface climatic variables. Compared with domestic observations, it has some merits concerning China climate change over the 20th century. Firstly, this dataset provides new information of the climate change over western China before 1950. Although it should be noted that the records are interpolated from observations, the results show significant correlation with the observation in the second half of the 20th century. Secondly, CRU dataset provides monthly mean fields, while domestic centuryscale series is just annual mean or seasonal mean data in the first half of the 20th century. Moreover, there are not any proxy data included in the construction of this dataset, which can bring noise and uncertainty. Hence, comparison between the CRU dataset and domestic observations is the way to verify the characteristics of China climate change during the 20th century and to validate the quality of the dataset in both China and UK. The results are as follows： （1） The interannual temperature variation is identical in both datasets. Their positive correlation coefficient is 0.84. They slightly differ from each other in the 1920s, when CRU underestimates the warming change in China, and therefore overestimates the warming trend of the whole century. （2） Even in the given 10 regional scales, both CRU and domestic data exhibit good consistency, apart from Tibet and Xinjiang areas. About one celsius degree bias is estimated by CRU in Tibet during the 1920s, which is the major difference from the reconstructed record. （3） The seasonal variability of precipitation over eastern China is identical in both series. The highest correlation coefficient （0.93） for 100 years among the four seasons is in autumn, while winter is the season that their correlation is the lowest one （0. 77）. （4） CRU data exhibits appropriate interdecadal variation of temperature and precipitation as shown in China records. Particularly, CRU dataset also presents some primary features before 1951, especially in western China, where and when no observational data can be available. Therefore, CRU high resolution grid data present a more complete picture of climate change in China over the 20th century.

Key words:China climate, the 20th century, high resolution, temperature, precipitation

The below is a paper discussing the relationship between CRU data covering China and Chinese meteorological and historical data during the last 100 years. There is excellent agreement (0.84) between these annual two independent (before 1950) temperature series. 英国CRU 高分辨率格点资料æ?­ç¤ºçš„20 世纪中国气候å?˜åŒ– – æ¯?组 2 个 »
闻新宇， 王ç»?武， 朱锦红 – 大气科学, 2006 – scholar.ilib.cn
万方数�资�系统. 大气科学 CHINESE JOURNAL OF ATMOSPHERIC SCIENCES 2006

Why not just preempt the inevitable refusal and ask him to consider your inquiry as being a request under the Freedom of Information Act/Environmental Information Act?

Enclosed are (1) a comparison of the HadCRU3 27.5N, 117.5E gridcell (red) against the corresponding NOAA gridcell (black), both in annualized form, showing a substantial difference prior to 1940; (2) a comparison of the same gridcell (shown here as black points) against all 20 GHCN v2 stations in the gridcell converted to annual anomaly format. Fuzhou is the light grey value in the early part of this series.

I’ve consulted the publication Brohan et al 2006, but it sheds no light on the matter. Could you clarify what stations contributed to this gridcell calculation, whether the station versions used match the versions presently archived at GHCN v2 and what adjustments, if any, were carried out on the station data?

Thanks for your attention, Steve McIntyre