I was surprised by the shrill headlines from a British newspaper with the old fashioned name the Telegraph: “The fiddling with temperature data is the biggest science scandal ever”. So what is this all about?

The story makes serious allegations, however Victor Venema explains why the Telegraph got it wrong in Variable Variability, and makes the point that three hand-picked stations from Paraguay – out of thousands – hardly matters. He also shows the effect of post-processing on the global mean temperature: it reduces the global trend compared to raw data.

The story also sparked some discussion between colleagues at the Norwegian Meteorological Institute, where I work, as several of us know the scientist cited in the paper quite well. It would be completely out of character that he’d endorse the views expressed in the article, and this is also what he conveyed to us.

The records show that the recent high temperatures on Iceland are unprecedented, contrary to the main message from the Telegraph. And the evidence is not just in the temperature, but in a wide range of observations.

I like to look at the numbers myself, especially since the journalist responsible for the Telegraph story, Christopher Booker, bases some of his allegations on climate records with which I have some experience. Booker dismisses the data records and claims that

weather stations across much of the Arctic, between Canada (51 degrees W) and the heart of Siberia (87 degrees E). Again, in nearly every case, the same one-way adjustments have been made, to show warming up to 1 degree C or more higher than was indicated by the data that was actually recorded.

It is implied that such adjustments have been made to the Goddard Institute for Space Studies (GISS) data as well as the data from the National Climate Data Center (NCDC).

The purports about systematic one-way adjustments can easily be tested by comparing the trends in the GISS data with the independent North Atlantic Climate Data (NACD) or a more recent temperature analysis for Svalbard by Nordli et al. (2014).

It is straightforward to test Booker’s claim with open-source methods and data (see R-srcipt), and when we compare the independent Svalbard temperature from Nordli et al (2014) with GISS, we see that the GISS data has a smaller annual mean trend than the independent Norwegian data set for the same years (Figure 1).

But is Svalbard representative for the this part of the Arctic? We can repeat the exercise for the most important temperature records from this region, and it is clear that there is no one-way adjustment, as purported in the Telegraph (Figure 2). In other words, our inspection of the actual data shows that Booker’s claim is false.

Another question is why there are differences between the different data sets. The GISS data are mostly taken from raw world weather records that have not been subject to the same quality control and homogenisation as the NACD or the Svalbard temperature of Nordli et al (2014).

Homogenisation is needed to remove effects from non-climatic artifacts, such as a change in the formula over time for estimating monthly mean values. Other conditions may include relocation of the thermometer, urban encroachment, or replacement of the instruments. GISS uses the GHCN adjustments, rather than doing it itself, but the way the GHCN corrects for artifacts may be different to the local met services.

Booker also accuses GISS and NCDC of using

“the warming trends to estimate temperatures across the vast regions of the Earth where no measurements are taken”.

A bizzare claim, and one may wonder why it seems so natural for Booker to make associations with misconduct. George Monbiot, on the other hand, has referred to him as a charlatan bent on spreading misinformation. In any case, a person who writes such a misleading story shows little respect for his readers.

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