For those too busy or too lazy to read this entire post, here is the main conclusion: comparing raw versus homogenised temperature records from KNMI’s main station de Bilt shows that the applied adjustments cool the past. More precisely, summer temperatures of 1900-1950 have been cooled to such extent that certain claims (like the summer of 2003 being the hottest on record) are only supported by the adjusted data set, and not by the raw data set. Furthermore, comparing raw versus homogenised data reveals that the correction for the urban heat island (UHI) effect is no longer being applied after 2006, while the reason for cancelling this correction is not provided.
First two small disclaimers: first of all, I am a biomedical scientist, not a climatologist. However, I am confident that my scientific skills allow me to correctly reconstruct changes between raw and adjusted temperature records. Here I only describe what has been changed in an adapted temperature data set, not why and how it has been changed, so in this post I will not really enter the realm of climatology (I will leave that for future posts…). Secondly, I am a scientist, not a journalist. So I analyse data freely supplied to me, but I do not necessarily correspond with the data source to learn their view on my analysis and interpretations. Lees verder “KNMI temperature homogenisation: cooling the past”