Mora said the threshold to deadly conditions caries from place to place, with some people dying in temperatures as low as 23C. A crucial factor, he said, was the humidity level combined with the heat.“Your sweat doesn’t evaporate if it is very humid, so heat accumulates in your body instead,” Mora said. “People can then suffer heat toxicity, which is like sunburn on the inside of your body. The blood rushes to the skin to cool you down so there’s less blood going to the organs. A common killer is when the lining of your gut breaks down and leaks toxins into the rest of your body.”
Global warming is a potent instigator of deadly heat, with research from University of California, Irvine this month finding the probability of a heatwave killing in excess of 100 people in India has doubled due to a 0.5C increase in temperature over the past 50 years.“The impact of global climate change is not a specter on the horizon. It’s real, and it’s being felt now all over the planet,” said Amir AghaKouchak, UCI associate professor and co-author of that study.“It’s particularly alarming that the adverse effects are pummeling the world’s most vulnerable populations.”
Elevated temperatures and dry conditions have been exacerbated by the clearing of trees, which provide shade and cooling moisture, in urban areas. Mora said that while adaption such as government heat warnings and the increased use of air conditioning has helped reduce deaths, this was not a viable long-term solution.“The heat means that we are becoming prisoners in our own homes – you go to Houston, Texas in the summer and there’s no-one outside,” he said.“Also, the increased use of air conditioning means that electrical grids fail, as has happened in New York City, Australia and Saudi Arabia. We need to prevent heatwaves rather than just trying to adapt to them.”
The Guardian, June 2017 – Lethal Heat Risk Rising in the UK
Public Health England warned on Friday before the high temperatures over the weekend that “for some people, such as older people, those with underlying health conditions and those with young children, the summer heat can bring real health risks”.
It drew attention to the Heatwave Plan for England, published in May 2015, noting that there were about 2,000 “excess deaths” during the heatwave in August 2003, with 680 more in summer 2006 and 300 killed in 2009.
The lethalness of heatwaves is often hidden because the total number of deaths is not reported until many months after they have happened.
In its annual report last November on deaths over the previous 12 months, an analysis by the Office for National Statistics (ONS) showed that, while there were markedly more deaths during the winter, a spike in casualties was evident on 19 July 2016.
On that date, there were 1,661 deaths recorded in England, compared with the five-year daily average of 1,267. The ONS pointed out that this peak coincided with the hottest day of the year, with maximum temperatures of 31C in some parts of the country.
Public Health England on Monday raised the level of its “heat-health watch” in anticipation of further hot weather this week, with the Met Office forecasting daytime temperatures of more than 30C across parts of the country.
The level-three amber warning, one level below a national emergency, advises people to stay out of the sun, keep homes cool, and check that anyone “at special risk” knows how to cope with the conditions.
However, the Committee on Climate Change has highlighted a worrying lack of understanding of heatwave risks which is increasing the number of people that succumb in hot weather.
The 2014 progress report to parliament by its adaptation sub-committee found that heat contributes to about 2,000 premature deaths each year in the UK, and that this figure could rise to about 7,000 annually in the 2050s due to the impact of climate change and population growth.
It concluded that “the uptake of measures to increase cooling capacity in existing homes is currently very low”, and suggested that this may be because “the public appear to perceive that heatwaves and hot weather have become less common over time”.
It cited research on a representative sample of the UK public who believed that hot weather had become less common during their lifetimes.
The study did not explore the influence of coverage of extreme weather by the UK media. Many national newspapers and broadcasters have downplayed the risks of heatwaves and flooding by amplifying the false claims of climate change scepticsthat there has been no increase in extreme weather events.
Nevertheless, the Met Office has indicated that the UK appears to be warming more quickly than the global average and refers to research showing that “the maximum daily temperature and minimum daily temperature in the UK have risen by just over 1C since the 1950s”, adding that “there is a suggestion that the warmest daily temperature extremes are rising faster in summer, whereas the coldest daily temperature extremes are rising faster in winter”.
In its assessment two years ago of the government’s National Adaptation Programme, the Committee on Climate Change warned that “there is low awareness amongst the general public about how the risks from heat are changing”.