{"id":426268,"date":"2026-02-15T12:18:37","date_gmt":"2026-02-15T11:18:37","guid":{"rendered":"https:\/\/climatescience.press\/?p=426268"},"modified":"2026-02-15T12:18:39","modified_gmt":"2026-02-15T11:18:39","slug":"the-data-dutch-meteorological-institute-reinstates-early-20th-century-heat-waves-it-had-erased-earlier","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=426268","title":{"rendered":"The Data: Dutch Meteorological Institute Reinstates Early 20th Century Heat Waves It Had Erased Earlier"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

From The No Trick Zone <\/a><\/p>\n\n\n\n

By\u00a0P Gosselin<\/a><\/em><\/p>\n\n\n\n

Victory for climate skeptics, science in the Netherlands\u2026erased historical heat waves get reinstated<\/strong><\/p>\n\n\n\n

The Clintel (Climate Intelligence) reports that the KNMI (the Royal Netherlands Meteorological Institute) has reinstated seven historical heatwaves from the pre-1950 era<\/a> that had previously been \u201cerased\u201d from official records due to statistical adjustments.<\/p>\n\n\n

\n
\"\"
Tropical days at De Bilt, version 0, 1 and 2 (staves) with non-linear trendline (orange solid line).
The trendline was calculated by the LOESS-function with span=20 points. Source:\u00a0Clintel<\/a><\/em><\/figcaption><\/figure>\n<\/div>\n\n\n

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.<\/p>\n\n\n\n

KNMI had overcorrected the data \u2013 cooling the past<\/strong><\/p>\n\n\n\n

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

    \n
  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<\/li>\n\n\n\n
  2. The KNMI used short comparison periods, which skeptics claimed introduced bias.<\/li>\n<\/ol>\n\n\n\n

    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<\/em>) in 2021. They demonstrated that by using different, more robust parameters\u2014such as comparing De Bilt to more than one station and using longer timeframes\u2014the number of \u201ctropical days\u201d (above 30\u00b0C) was significantly higher than the KNMI\u2019s adjusted figures.<\/p>\n\n\n\n

    Following years of pressure and the peer-reviewed publication, the KNMI updated its homogenization method. According to the article, the KNMI\u2019s new analysis\u2014which now uses multiple reference stations (Eelde and Maastricht) and longer 15-year comparison periods\u2014has resulted in the reinstatement of seven of the lost heatwaves.<\/p>\n\n\n\n

    Significance: more nuanced view of warming<\/h3>\n\n\n\n

    The is a major victory for climate skeptics and a \u201cpoint of principle.\u201d It restores several intense heatwaves (such as those in 1911, 1947, and 1948) to the official Dutch record.<\/p>\n\n\n\n

    Clintel proves that official climate \u201chomogenization\u201d can be prone to errors that exaggerate the warming trend by cooling the past.<\/p>\n\n\n\n

    The authors note that while the \u201cdisappearance\u201d 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.<\/p>\n\n\n\n

    The reinstatement of the heatwaves shows that the KNMI has admitted that its previous adjustments had been too aggressive.<\/p>\n\n\n\n

    Full Clintel article<\/a>.<\/p>\n\n\n\n

    <\/p>\n","protected":false},"excerpt":{"rendered":"

    Victory for climate skeptics, science in the Netherlands\u2026erased historical heat waves get reinstated<\/p>\n","protected":false},"author":121246920,"featured_media":426273,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","_crdt_document":"","advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1],"tags":[691825589,691820751,691841397,691841395,691823438,691819908,691841396,691833509,691840977],"class_list":{"0":"post-426268","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","6":"hentry","7":"category-uncategorized","8":"tag-climate-skeptics","9":"tag-clintel","10":"tag-cooling-the-past","11":"tag-dutch-meteorological-institute","12":"tag-marcel-crok","13":"tag-netherlands","14":"tag-peer-reviewed-journal-theoretical-and-applied-climatology","15":"tag-royal-netherlands-meteorological-institute-knmi","16":"tag-warming-trend","18":"fallback-thumbnail"},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/02\/AQO3J7syICTURDr04nuzDp7xaPj6NQqyE9PEq-7WrtKxR7CYW8fOsbYErHlGeXE-9ItKJehYFREheVU1Ug3QN07UhixMlDopKqRS2HoYlK-bAU3mLl_eCuLezUWUk4MR.jpeg?fit=1713%2C945&ssl=1","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-1MTi","jetpack-related-posts":[{"id":424744,"url":"https:\/\/climatescience.press\/?p=424744","url_meta":{"origin":426268,"position":0},"title":"Dutch climate skeptics vindicated: KNMI reinstates seven pre-1950 heatwaves after long battle","author":"uwe.roland.gross","date":"02\/05\/2026","format":false,"excerpt":"Seven years after Dutch skeptics first challenged KNMI\u2019s temperature adjustments, the institute has reinstated seven \u201clost\u201d pre-1950 heatwaves at De Bilt \u2014 validating claims of over-correction that had erased 16 out of 23 historical extremes. 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