所以英国议会问：How independent are the other two international data sets?

IOP的回答是：Published data sets are compiled from a range of sources and are subject to processing and adjustments of various kinds. Differences in judgements and methodologies used in such processing may result in different final data sets even if they are based on the same raw data. Apart from any communality of sources, account must be taken of differences in processing between the published data sets and any data sets on which they draw.

统计气候数据涉及到四维时空分布，可以想像其难度。从气候门邮件、以及Jones本人最近的采访，都可以看出CRU的数据和处理并不那么清晰。