Compared to our European neighbours, Ireland’s conditions could be described as a mild heatwave – until you add in the heavy humidity load.
Scientists have warned that temperature data alone doesn’t tell the full story of how hot weather affects human health.
“What we really need to talk about is wet bulb temperature (WBGT), an index that combines radiant heat with air temperature and water vapor pressure,” said Professor Mike Tipton.
He is a professor of physiology at the University of Portsmouth’s Extreme Environments Laboratory and is better known in Ireland for his connections with the Waterford Institute of Technology, where he has given a guest lecture on the opposite topic of cold water immersion and its effects on drowning.
The WBGT number crunches how hot and how humid it is, pinpointing the safe, difficult, and downright dangerous combinations.
“You can be in a cooler environment with higher humidity, which is actually more stressful on the body in terms of heat loss, because our main route of heat loss is through evaporation of sweat,” he explained.
“That’s us now [in the southern UK] at a temperature known as the critical environmental limit.
“At around 40 degrees Celsius and around 45 percent humidity, people warm up as they go about their daily activities and walk around the house.”
Lower the former but raise the latter and you get the same effect.
At around 35°C wet-bulb temperature, sweat does not evaporate and people who cannot find other ways of cooling are exposed to severe and deadly heat stress.
These conditions were met in Pakistan last year and are likely to become more common. Ireland is unlikely to replicate the conditions in Pakistan any time soon, but Prof Tipton explained how quickly people can overheat.
“Eighty percent of the energy expended by metabolic exercise is released as heat, allowing you to go from 90 watts at rest, which is equivalent to a lightbulb in terms of heat production, to a 2-kilowatt fire when you’re exercising hard .”
To put it really simply, he warned people to drop their exercise routine for a few days and just be a lightbulb.
There has been some resistance here over warnings from public health and safety agencies about sensible behavior in high temperatures, with some people taking offense at the idea that they cannot be trusted to think for themselves.
But at the heatwave briefing of scientists Prof Tipton spoke at yesterday, a common theme was the importance of effective communication with the public.
Professor Hannah Cloke, a natural hazards researcher at the University of Reading, who has also lectured on Irish flood forecasting here, first looked to her own profession.
“We still have people shrugging their shoulders and saying this is only summer, so we need to work better at communicating the dangers of heatwaves better.
“Last year’s heatwave in the UK killed at least 10 times as many people as the Grenfell fire, so we need to start thinking about heatwaves in a very different way.”
She said it’s difficult to convey why a temperature number isn’t enough to get the message across, which could explain why some people here aspire to be fireworks rather than lightbulbs.
“We’ve been working quite a bit on how to combine other important things, like B. Humidity with temperature to create a sort of “feels like” temperature index.”
It could work the same way as the wind chill factor, giving people a better sense of how cold it really feels and what they need to do to protect themselves.
In Ireland yesterday the consensus was that it was muggy, heavy and harsh, but humidity was only low to moderate.
So while the Feels like index is still developing, we felt lucky not to be in the UK or mainland Europe.
https://www.independent.ie/irish-news/temperature-alone-does-not-tell-the-full-story-as-its-humidity-that-makes-heat-harder-to-tolerate-41850170.html The temperature alone doesn’t tell the whole story as it is the humidity that makes the heat harder to bear