Ellen Phiddian
Cosmos science journalist
Next time you are recovering from a wild storm, and feeling the need for a wonderful revitalising cup of tea, don’t be surprised if it doesn’t give you the warmth inside you were hoping for. The storm might have changed the way tea tastes.
In November 2023, Storm Ciarán rolled across Europe, causing flooding and wind damage from Ireland to Italy.
It also, according to a new study, dropped the boiling point of water low enough to degrade black tea quality in south-east England, right around breakfast time.
The study, published in Weather, reports that the air pressure in Reading, UK, dropped so low that water boiled at just under 98°C, which is often considered below the minimum for an ideal cup.
“The effect of pressure on boiling temperature is long known to mountaineers, but Ciarán brought the effect to a wide region,” says study co-author Dr Alec Bennett, a meteorologist at Bath Spa University, UK.
The boiling point of liquids changes with pressure. At normal atmospheric pressure, this is around 100°C.
But storms bring with them dramatic drops in air pressure, which means that water changes from a liquid to a gas at lower temperatures. Storm Ciarán had unusually low air pressure, setting records in some parts of England.
“As an experimentalist, I saw the opportunity to make some measurements of the properties of boiling water during low atmospheric pressure,” says co-author Caleb Miller, a PhD student at the University of Reading, UK.
Armed with a temperature sensor and a kettle, the researchers tracked the boiling point of water as the storm passed over Reading.
They combined this with data from weather stations across the UK to track the storm’s movement. The centre of the low pressure system moved across England between 4am and 10am – or, as the researchers point out, breakfast time.
The boiling point of water dropped to just under 98°C in the lab, and the weather data suggests this happened across much of the country.
This may have been enough to change the flavours of the tea, according to the researchers.
“The small changes in boiling point seem more likely to be sensed by these means than the others we considered,” lead author Professor Giles Harrison, also from the University of Reading, tells Cosmos.
“This does highlight that the atmosphere – and changes in it – may have influences in unexpected ways.”
The researchers also point out that unusually high pressure, which is usually accompanied by still, sunny weather, can raise the boiling point of water – at one measurement they took in January 2020, the boiling point at the same station rose to nearly 101°C.
