Extreme weather is becoming increasingly common, and, if humans are to survive, they must adapt to climte change. Becky McCall explains

During the first 20 days of August 2003, 14,802 people died in France and 2,000 in England as temperatures remained relentlessly high. In France, thermometers consistently recorded temperatures above 40C. The number of deaths was up to 70 per cent higher than normal for the time of year.

Britain had not experienced such extreme weather since the summer of 1976, but climate change experts believe these events will become far more common if global warming continues. It is predicted that, by 2050, a heatwave like that of 2003 could occur on average every five to six years. By 2080, it could be as often as every other year.

Extreme weather is becoming increasingly common around the world, which has prompted a flurry of research interest into how we can adapt our health infrastructure to cope. The Department of Health's Expert Group on Climate Change and Health is publishing a report this week on the consequences of extreme weather, such as the spread of infectious disease and food poisoning.

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Sani Kovats is a member of the group and a lecturer in environmental epidemiology at the London School of Hygiene and Tropical Medicine. As an epidemiologist, Kovats takes a keen interest in mortality patterns related to extreme weather.

"Many of the deaths (in 2003) were due to underlying chronic conditions such as cardiovascular or respiratory problems, but some, in France, were simply due to heatstroke that went untreated for too long. Part of the problem is that people don't recognise early enough that someone has heatstroke, and by the time they do it is too late," he says.

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Humans function optimally at 37C. If our body temperature exceeds this, we sweat. As moisture evaporates from the surface of the skin, we cool down.

If we become dehydrated as a result of loss of fluid through sweating, circulation of blood to the skin diminishes and sweating ceases. Then, like an oven without a thermostat, we overheat.

"Many of the deaths observed during the 2003 heatwave were in people whose ability to sweat was compromised," Kovats says. "Many mental health drugs interfere with sweating, as do other drugs for chronic conditions. Another group of people vulnerable to heatwaves are those with behavioural problems that inhibit their response to protect themselves from the heat, for example, alcoholics or those with severe mental illness," he adds.

Bill Keatinge, emeritus professor of physiology at University College London, believes that so many lives were lost in France during the 2003 heatwave because people did not realise that they needed to cool themselves down or did not know how to. Instead, they called the emergency services, which were overwhelmed. "Severe heat stress produces a direct and immediate threat. If outside temperature and humidity overwhelm the body's capacity to lose heat, body core temperature rises. At about 41C this starts to cook, or denature, the body tissues. Once that happens to vital organs, the person will not recover," Keatinge says.

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Many of the deaths could have been prevented with simple measures. Opening windows during the cool hours of morning, drinking lots of water and eating food rich in salt are basic tactics.

The 2003 heatwave demonstrates that climate adaptation needs to cover behaviour and physiology as well as issues such as the design of buildings and transport. Education will be key, as research shows that people are not making the long-term behavioural changes necessary to adapt to climate change. At the United Nations Climate Change conference in December, Irene Lorenzoni, a researcher based at the Centre for Environmental Risk at the University of East Anglia, told a meeting that while people respond short term to events, they fail to adapt their behaviour over the long term. She called for more resources to promote climate adaptation.

Diana Liverman, director of the Environmental Change Institute at Oxford University, echoes the call. She says there is an urgent need for people to "'mainstream' adaptation to climate change in their plans and decisions" and to try to reduce global warming. In Britain, she says, this will mean not only re-evaluating healthcare, but also rethinking our approach to conservation and landscape preservation as native species shift northwards.

Readjusting management of water resources and rethinking foreign assistance "to include adaptation in our policies towards poorer countries and to support international efforts to establish a just framework for adaptation and the funds to implement it" must also be considered.

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The latest DH report is part of the effort to raise people's awareness of climate adaptation. It builds on Heatwave: Plan for England , published in 2004. Mike Gill is regional public health director for the South East and architect of the plan. He has been working on this year's report, which incorporates advice based on research into vulnerable groups. "Our recent research has shown that certain members of society are more vulnerable than others, in particular those in care homes, who show an increase of 50 per cent (in death rates in England) and 100 per cent in France. Our new report addresses this. We would like to see heatwave planning parallel the type of planning that is being put in place for pandemic flu," Gill says.

According to the Met Office, a heatwave response is triggered by a rise above threshold day and night temperatures, which vary by region. The average daytime temperature is 30C, at night it is 15C. Gill says that this year is predicted to be average, if not cooler than the past couple of years. But he is not complacent - heatwaves have devastating consequences precisely because people are taken unawares. Extreme weather events are difficult to predict. The only thing we can be certain of is that if climate change continues at the current rate, there will be a lot more of them.

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