How to keep cool: your burning heatwave questions answered

<span>Photograph: James D Morgan/Getty Images</span>
Photograph: James D Morgan/Getty Images

As parts of Britain swelter in near-record temperatures, we answer some of the burning questions you may have.

How big a factor is global heating?

Extreme weather events have become more frequent in recent years as a result of global heating. Last week, scientists said July was on track to be the hottest month ever measured on Earth, while last month was the warmest June ever recorded. Early projections suggest 2019 is likely to be the second warmest year ever recorded, after only 2016, which was boosted by El Niño weather system.

Nine of the 10 hottest years on record have occurred since 2000, according to the US National Oceanic and Atmospheric Administration.

Although it is too early to pinpoint the extent to which the current UK heatwave was caused by global heating, scientists found the June heatwave across Europe was made at least five times likelier by the climate crisis, while last year’s summer heatwave in the UK was made at least 30 times more likely.

Prof Michael Mann, a prominent climate scientist at Penn State University, said last year that asking if climate change “causes” specific events was the wrong question. “The relevant question is: ‘Is climate change impacting these events and making them more extreme?’ And we can say with great confidence that it is.”

The impacts of climate breakdown are not limited to extreme heat – it is also making the weather more unpredictable and more extreme. The warming of the atmosphere results in more water evaporating from the oceans, meaning hurricanes are growing more intense, and prolonged periods of rainfall and floods are becoming more common.

Although it is not yet conclusive, many scientists also believe climate breakdown is weakening the jet stream, which could be partly to blame for extended periods of extreme cold, such as last year’s polar vortex in the US or the 2018 “Beast from the East” that brought heavy snow to the UK in March 2018. AE

How do you stay cool?

Experts recommend staying in as well-ventilated environments as possible, while avoiding alcohol and exercise and drinking plenty of water.

“If outside, wear loose, thin, porous, light-coloured long-sleeved clothing,” said Prof Hugh Montgomery, from UCL’s division of medicine. “This allows air movement, limits insulation, allows sweat to evaporate and reflects light and heat.”

Wearing a light, open fabric sun-hat can also help, he added. Outside, something as simple as consciously breathing can also help regulate the nervous system and cool you down.

While inside, the NHS suggests keeping windows closed and using light-coloured curtains. “You can open the windows for ventilation when it is cooler,” the health service advised.

Prof Mike Tipton, from the University of Portsmouth’s extreme environments laboratory, said that immersing your hands and feet in cool water was an effective way to lose heat.

“Artificially cool with fans. You can also enhance evaporation cooling by misting the body with water,” he said, alluding to the increasingly popular hydrating products which you spray in your face.

He also recommended checking your urine colour was a pale straw colour, which indicates adequate hydration.

When preparing for bed, others recommended briefly putting your bed sheets and pillows into a plastic bag and placing them in a freezer, as well as freezing cold water in a hot water bottle to cuddle.

“That’s a very useful way of trying to keep your bed a little bit cooler for longer, or at least enough time for you to drift off to sleep,” Dr Guy Leschziner, a neurologist at Guy’s and St Thomas’ hospitals, told BBC Radio 4’s Today programme.

In contrast to some commonly held beliefs, he also advocated wearing clothes to bed.

“People may be better off sleeping in clothing rather than sleeping naked,” he said. “If you’re wearing a natural fabric like cotton, then it acts as a wick for your sweat and acts as a surface area for it to evaporate, and thus may make you much cooler.” MB

How is the economy affected?

The heatwave is providing some respite for the high street as demand rockets for sundresses, electric fans and sprinklers. But experts have warned the burst of sunshine has arrived too late to save summer for some struggling chains.

John Lewis said it was selling six fans a minute, with handheld ones particularly sought after as Britons tried to keep cool on the go. Sales of hoses and sprinklers were up nearly 60% on last week with demand for paddling pools surging more than 40%, the department store said.

But after last year’s long hot summer many retailers are struggling to match stellar sales figures achieved in 2018. On Tuesday, the grocery market analysts Kantar said UK supermarkets sales had fallen for the first time in three years in the 12 weeks to 14 July as the cool start to the season hit sales of soft drinks, alcohol and ice-cream.

Analysts suggested the hot spell would help retailers clear unsold seasonal products such as paddling pools and barbecues but had arrived too late for fashion retailers who were already holding sales, meaning any pick up in trade was less lucrative than it would have been earlier on.

“A heatwave affects different parts of the retail market in different ways,” explained the independent retail analyst Richard Hyman, who cautioned very hot weather would deter people from visiting the high street. “Food sales will go up because it is one of those areas that is most sensitive to spikes in the weather … but the summer [fashion] sales are nearer to their end than beginning.”

While the sunshine may provide a shot in the arm for some businesses, scientific studies have shown that high temperatures can knock the wider economy as productivity – the amount of economic output generated per hour worked – falters. Academics believe higher temperatures in hot countries can lower economic growth, but boost output in cold countries, with shifts of about 3-4% of GDP per degree celsius in both directions.

When temperatures rise, crop yields fall. People take more time off, which leads to lower output, while concentration levels drop and mistakes are more likely. According to researchers at the University of Helsinki, the optimum temperature for office productivity is between 22C and 25C. Hotter than this and productivity falls, by as much as 5% at 28C. ZW

Is it hot everywhere?

While the south of England swelters, temperatures in Scotland have not soared to such extremes, with Glasgow and Edinburgh in the central belt, as well as Aberdeen and Inverness further north, registering between 20C and 23C after a humid and stormy night.

Lightning strikes overnight disrupted rail services in the Highlands, with passengers delayed because of damage to the signalling system between Inverness and Beauly.

Occupants of a house struck by lightning in the village of Markinch, in Fife, escaped injury after a roof fire was sparked by thunderstorms, which intensified after 4am.

The Met Office warned that storms would continue to affect Scotland throughout Wednesday. The east coast of Scotland is expected to see more sunshine, with cloud clearing for a bright afternoon. LB