Luke MINTZ

Heatwaves are here to stay, so will we have to get used to being sweaty and uncomfortable in bed? Luke Mintz asks the experts

There is something cruel about a stiflingly hot night. We toss and we turn, abandon our duvets, crank open our windows and turn on the fans. Our slumber suffers, with the heat showing “significant effects on sleep calmness, difficulty in falling asleep, sleep satisfaction, and sleep adequateness”, according to a study published in China last year.

All of this will sound familiar for anybody in south-east England who has spent much of the last week in a burning bedtime sweat. The region has been hit by a heatwave, with daytime temperatures reaching 36C (97F) in some parts, prompting wildfires in Surrey; and nighttime temperatures reaching 22C (72F). “It’s so hot,” went a popular joke on Twitter, “that a Tennessee Williams play is about to break out in my room” – a reference to the playwright’s gift at conveying the long, sweltering nights in his native Mississippi.

It will come as bad news, then, that “tropical nights” – defined by meteorologists as a night in which the temperature at no point drops below 20C (68F) – are becoming more common in the UK. Between 1961 and 1990, forecasters recorded only 44 tropical nights – an average of about 1.5 per year, according to the Met Office. But there were five in 2018 alone, and four in 2019. So far in 2020, we have already endured five of these uncomfortable nights, four of which occurred in south-east England in the last week (the other was on June 25).

And, in another sign of how this summer is becoming evermore “tropical”, thunderstorms are now forecast across much of the UK for the next few days, albeit with the overnight temperatures expected to stay high in some parts.

Tropical nights are currently still concentrated in the south-east, with only three recorded in Scotland since 1961, and zero in Northern Ireland over the same period. But the Met Office expects them to spread more widely in coming years.

“Tropical night temperatures can be extremely challenging for those with underlying health conditions,” says Grahame Madge, a Met Office spokesman. “When overnight temperatures remain high, it is hard to get any respite and rest before the next day’s heat begins to build.”

According to behavioural psychologist Dr Sophie Bostock, tropical nights make it hard to sleep by disrupting our circadian rhythm. Cooler temperatures at dusk, she says, act as a “cue” for our bodies to become drowsy, by pushing blood to our extremities (hands, feet, the tops of our heads), helping to release heat. If no such cue arrives, then sleep becomes a struggle.

It is usually controversial to attribute any specific weather event to climate change, but scientists of virtually all stripes agree that the increasing frequency and intensity of heatwaves can be blamed on carbon emissions.

“We will have to get used to these kinds of summers,” said Oxford University’s Dr Friederike Otto during the particularly hot World Cup summer of 2018. “There is no doubt that there is a link to climate change.”

So, what can be done? How can we future-proof ourselves against the invasion of tropical nights? One obvious answer is air-conditioning, which since its invention in 1902 has made life bearable in some parts of the world, facilitating population explosions in Dubai and along American’s sun belt, and allowing the construction of glass-fronted skyscrapers – previously too hot to live or work in.

It can cost thousands to install, and with tropical nights still reasonably rare in Britain, most homeowners have decided against it: the last large survey, in 2008, found that just one in 200 UK homes enjoyed any kind of air-con. (Not to mention that it has its own environmental impact, and is responsible for about 12 per cent of carbon dioxide emissions in the global building sector, according to the International Energy Agency).

‘It is very difficult to get any rest before the next day’s heat begins to build’

‘It’s so hot that a Tennessee Williams play is about to break out in my room’

But minds could be changing. Last year, Parliament’s environmental audit committee predicted that “air conditioning is likely to become widely used in the UK to reduce heat vulnerability”, and called for the Government to grant subsidies as our summers grow more gruesome.

Gary Clark, chairman of the Sustainable Futures Group at the Royal Institute of British Architects, thinks that architects should take tropical nights into account when building new homes. In a “rush” to design well-insulated buildings that are primed for winter, he said, “quite a lot of people have forgotten about overheating”. His group recommends French windows, underfloor cooling, and window shades on the outside rather than the inside to help with ventilation.

Essentially, there is no reason that we Brits need to accept sleepless tropical nights. But, in the meantime, it can’t hurt to buy a few fans.