From The No Trick Zone

By P Gosselin

Victory for climate skeptics, science in the Netherlands…erased historical heat waves get reinstated

The Clintel (Climate Intelligence) reports that the KNMI (the Royal Netherlands Meteorological Institute) has reinstated seven historical heatwaves from the pre-1950 era that had previously been “erased” from official records due to statistical adjustments.

In 2016, he KNMI updated its historical temperature data for the De Bilt weather station (the national reference point). Using a process called homogenization, they had adjusted old temperature readings downward to account for changes in measurement methods and station relocation. This process effectively removed 16 out of 23 recorded heatwaves between 1901 and 1951, leading to the public narrative that heatwaves were much rarer in the past than they are today.

KNMI had overcorrected the data – cooling the past

A group of four researchers associated with Clintel, led by Marcel Crok, challenged these adjustments. They argued that the KNMI had over-corrected the data. Their primary criticisms were:

1. The KNMI compared De Bilt with a station 150 km away (Eelde) using a method that was arguably unsuitable for such a distance, and
2. The KNMI used short comparison periods, which skeptics claimed introduced bias.

After the KNMI initially dismissed a 2019 report by the skeptics, the group published their findings in a peer-reviewed journal (Theoretical and Applied Climatology) in 2021. They demonstrated that by using different, more robust parameters—such as comparing De Bilt to more than one station and using longer timeframes—the number of “tropical days” (above 30°C) was significantly higher than the KNMI’s adjusted figures.

Following years of pressure and the peer-reviewed publication, the KNMI updated its homogenization method. According to the article, the KNMI’s new analysis—which now uses multiple reference stations (Eelde and Maastricht) and longer 15-year comparison periods—has resulted in the reinstatement of seven of the lost heatwaves.

Significance: more nuanced view of warming

The is a major victory for climate skeptics and a “point of principle.” It restores several intense heatwaves (such as those in 1911, 1947, and 1948) to the official Dutch record.

Clintel proves that official climate “homogenization” can be prone to errors that exaggerate the warming trend by cooling the past.

The authors note that while the “disappearance” of these heatwaves was used to support claims of unprecedented modern warming, their reinstatement provides a more nuanced view of historical climate variability in the Netherlands.

The reinstatement of the heatwaves shows that the KNMI has admitted that its previous adjustments had been too aggressive.

Full Clintel article.