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expert reaction to updated thresholds for UK heatwaves

The UK Met Office have updated the thresholds for heatwaves in the UK.


Prof Hannah Cloke, a natural hazards researcher at the University of Reading, said:

“The Met Office recalibration of the official heatwave definition for the UK shows how simple it is. It is an effort to maintain the idea that in the UK we call hot weather ‘a heatwave’ if it feels particularly hot, in the middle of the afternoon, for more than a couple of days in a row.

“With average temperatures rising across the UK, we have to shift the definition of what ‘particularly hot’ is, otherwise that definition becomes increasingly meaningless.

“There are benefits and downsides to having such a simple definition of a heatwave. It means that it is easier for people to understand. However, there are a series of different heat warnings, all triggered at different points to avoid heat impacts and deaths, depending on which nation of the UK you live in.

“People need to know what to do in advance and take action quickly when extreme weather is coming. If people don’t or can’t do anything to protect themselves against extreme heat, then people die. It doesn’t help to declare a ‘heatwave’ so often that people stop listening, but neither does having an array of poorly understood definitions of heat risk.

“As UK summers get hotter due to climate change, definitions will mean nothing at all if we continue to ignore the risks and fail to adapt our buildings and our habits to cope with the heat.”


Dr Radhika Khosla, Associate Professor at the Smith School of Enterprise and Environment, University of Oxford, said:

“Raising the bar for what counts as a heatwave has important implications for how people prepare (or don’t) for when temperatures are high. 28 degrees might be the ‘new normal’ in some parts of the UK, but we must be careful this doesn’t downplay the risks of heatwaves, which can be deadly for the vulnerable, elderly and very young. As overall temperatures rise in the UK due to climate change it’s also important to opt for sustainable cooling options that don’t contribute to making the problem worse.”


Prof Nigel Arnell, Department of Meteorology, University of Reading, said:

“This is further and clear evidence of how climate change is affecting our weather here in the UK. We have to get used to a ‘new normal’ – what we previously thought of as an unusually hot summer will soon become common. We have to make sure that our homes, offices and infrastructure can cope now with the anticipated higher temperatures so that we can reduce the ill-health and disruption that heatwaves produce. And things are only going to get worse. In a few years we’ll probably have to change the definitions again otherwise we’ll have a heatwave every summer. Reducing greenhouse emissions will slow the increase over the long term, but we need to better prepare for heatwaves now.”


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