Global warming is killing about 150,000 people a year, mostly in deprived and tropical areas, and the toll could rise dramatically if efforts are not made to combat climate change, the World Health Organisation (WHO) warned yesterday.
The United Nations agency said the health of millions of people was under threat as a consequence of rising temperatures and uncertain weather patterns, which many scientists claim are caused by greenhouse gas emissions.
The WHO said climate change could cause increases in malaria and other insect-born diseases, malnutrition and pollution-related diseases, as well as deaths from extreme one-offs such as this summer's heatwave in Europe.
The report, which has been published this week to coincide with the UN conference in Milan on climate change, blamed global warming for 2.4 per cent of diarrhoea cases and 2 per cent of all cases of malaria worldwide. It estimated that, by 2030, climate change could cause 300,000 deaths annually and that a further 5.5 million years of healthy living had been lost worldwide due to debilitating diseases caused by rising temperatures.
The report said: "The 1990s were the hottest decade on record and the upward trend in the world's temperature does not look like it is abating. In Europe this past summer, for example, an estimated 20,000 people died due to extremely hot temperatures."
Much of Europe suffered heavily in the heatwave because air conditioning is not common in homes, in part because of high energy costs. The conference heard on Wednesday insurance estimates which suggested that the European heatwave cost $10bn (£5.7bn). Hospitals in London had reported an increase in admissions of young children suffering renal problems. Dr Bettina Menne, a WHO hygiene specialist, said the problems were probably linked to dehydration during the heatwave.
The WHO said that installing air conditioning in homes, workplaces, hospitals or residences for the elderly would also risk increasing the emissions of gases from the burning of fossil fuels such as oil, gas and coal.
Kerstin Leitner, the WHO assistant director general, said: "There is growing evidence that changes in the global climate will have profound effects on the health and well-being of citizens in countries around the world."
The report said that even a rise of a few degrees in average annual temperatures could expose millions more people to the threat from malaria. This would be by both extending the malaria season in countries, where it is already endemic, and also by allowing the malaria mosquito to live in countries where, at present, it cannot survive, such as Europe. Other diseases spread by mosquitoes, such as dengue fever, could also increase.
Hotter and wetter conditions are also likely to increase the spread of diarrhoeal disease, which is particularly dangerous to children. And people living in deprived conditions who cannot afford proper refrigeration are more likely to eat food tainted with increased bacterial contamination, caused by higher temperatures. Countries which are heavily dependent on a predictable monsoon season for the cultivation of rice crops - such as India, Bangladesh and Burma - are more likely to suffer increases in malnutrition if the changes affect the reliability of the rainy season.
The report also said that increasing air pollution might lead to a rise in allergic conditions, such as asthma, and lung and respiratory complaints.