Concerns have been raised about the methodology used by the UK Met Office in recording temperature data, particularly regarding the use of sensitive electronic thermometers that capture short-term heat spikes.
Critics argue that these instruments, which can detect 60-second heat spikes, may produce readings that do not accurately reflect true atmospheric temperature changes.
For example, a temperature reading of 29.3?C at Kew Gardens on May 1st, 2025, was recorded at 2:59 PM, a value 2.6?C higher than the reading at 2:00 PM and 0.76?C above the reading one minute later.
Such rapid fluctuations are not typical of natural temperature changes, which generally vary by only 0.1?C to 0.3?C per minute.
The World Meteorological Organisation (WMO) recommends averaging temperature readings over five minutes to reduce short-term "noise" and standardise data.
However, the UK Met Office has been criticized for not following this practice, despite its role in WMO deliberations.
The use of electronic thermometers, which are more sensitive than older mercury-based models, is said to amplify these short-term fluctuations.
Mercury thermometers, which expand and contract in response to temperature changes, are less prone to such rapid variations because the movement of the liquid is physically constrained.
Further criticism focuses on the siting and classification of weather stations. Many Met Office stations are located in poor conditions, classified as CIMO Classes 4 and 5, which are considered unreliable with possible errors of up to 2?C and 5?C, respectively.
A study by Dr. Eric Huxter found that stations in lower CIMO classes exhibited greater average hourly temperature changes, suggesting that local environmental factors—such as nearby structures like greenhouses—may contribute to spiky readings.
Heathrow Airport, rated as a Class 3 site, was noted as an outlier with extreme temperature changes, possibly due to its location and surrounding infrastructure.
Additionally, the practice of using instantaneous peak readings—rather than averaged values—has been questioned. The Met Office's reported average temperature is calculated as the mathematical average of the daily maximum and minimum temperatures, but critics argue this method is flawed, especially in areas affected by the urban heat island effect.
The trend in recorded temperatures is said to be dominated by increases in minimum temperatures, which may not reflect genuine climate change but rather measurement artifacts.
Some claim that the use of such data serves to promote alarmist narratives about climate change, particularly in support of the Net Zero agenda.
In response to these concerns, a Freedom of Information request in November 2025 prompted the Met Office to reconsider its temperature reporting explanations, highlighting ongoing scrutiny of its data practices.
While the Met Office maintains its standards, the debate continues over whether current measurement techniques produce scientifically valid and reliable temperature records.