In the midst of a record-breaking low pressure caused by Storm Ciarán last November, millions of Britons were unwittingly forced to consume subpar cups of tea. The atmospheric pressure fell drastically, causing the boiling point of water to drop below the recommended 100C temperature for optimal flavor extraction from tea leaves. According to a study published in the journal Weather, the water in Reading was boiling at a mere 98C on the morning of the storm, a phenomenon made possible by the drop in atmospheric pressure.
For water to boil, the atmospheric pressure must match the vapour pressure of the liquid. It is common for atmospheric pressures to decrease during adverse weather conditions such as storms. On that particular day, the barometer plummeted to 956.0 millibars, the lowest recorded pressure since February 1989, and a reading that had not been seen for over 200 years in December 1821.
Effects of Storm CiaránCaleb Miller, a PhD student and co-author of the study, seized the opportunity to conduct experiments on the properties of boiling water under low atmospheric pressure. Utilizing temperature sensors and a standard electric kettle, Miller and his team collected data that would enable them to compare the results with previous boiling points observed under different air pressure conditions using the same apparatus. To gauge the broader regional impact of the storm on boiling points, the team combined weather data from various sources, including roadside weather stations across southern England and pressure readings from the Reading University Atmospheric Observatory.
The study revealed that the minimum pressure moved north-east across the region during the morning, coinciding with typical breakfast times, an occurrence rarely seen in densely populated areas. Alec Bennett, a co-author of the study, noted that the effect of pressure on boiling temperatures is well-known among mountaineers, but Storm Ciarán brought this phenomenon to a wide regional scale. The unfortunate bitterness of a nation’s tea was, therefore, a direct result of the record-breaking low pressure caused by the storm.