A few days ago, the Met Office admitted that Kew Gardens is a CIMO Class 5 site.
“Class 5 sites should not be used for climatological purposes, I look forward to the Met Office removing the spurious ‘record temperature’ from their website,” Paul Homewood writes.
The World Meteorological Organisation’s (“WMO’s”) Commission for Instruments and Methods of Observation (“CIMO”) establishes global standards for weather station siting and classification. Its classification system is a global framework that indicates how closely a weather station’s siting aligns with ideal exposure conditions.
The WMO is a specialised agency of the United Nations.
The Siting Classification for Surface Observing Stations on Land was formally introduced by WMO in 2014 and uses a Class 1 to Class 5 scale to assess the quality and representativeness of a site’s exposure for meteorological measurements like temperature, humidity and precipitation.
Class 1 represents an ideal, reference-grade site with wide-open exposure and minimal local influence, while Class 5 indicates an inappropriate environment with significant local obstructions or heat sources. It allows for broad international comparisons of data quality, with higher classes (1–2) indicating high confidence in data representativeness and lower classes (4–5) suggesting notable local exposure characteristics.
The Met Office internally rates stations as “Excellent,” “Good,” “Satisfactory,” or “Unsatisfactory,” and excludes Class 5 data from national climate records, while quoting Class 1–4 data....<<<Read More>>>....
