The heat wave which swept through Europe in the summer of 2003 pushed temperatures up 3.5°C higher than average, resulting in what was probably the hottest summer that region had experienced in 500 years. The journal Nature reports this month that during two weeks about 22 000 to 45 000 deaths* in the region were caused by this weather phenomenon. Most of these occurred among the elderly and infirm where heart and respiratory complications due to heat stress eventually proved fatal. Exposure to temperature extremes can be expected across the Western Cape as a warming trend sweeps the region in the next 50 years. These episodes could be exacerbated in cities where urban heat islands (where heat is trapped over cities due to a complicated interaction of evaporation processes, impervious surfaces and changed vegetative cover) could push the temperature up by 5 to 11°C on that experienced outside of the city. Economically marginal communities – which in many cases includes the farm labourers tending the Cape’s vineyards – are expected to be hardest hit as informal or poor housing is not insulated against the heat. The World Health Organisation and the United Nations Intergovernmental Panel on Climate Change predict that climbing temperatures and changing rainfall regimes will increase the spread of infection diseases such as malaria and dengue fever. The incidence of diarrhoeal disease and salmonella-related food poisoning can also be expected to climb while changing weather patterns will undermine food security, leading to malnutrition and increased vulnerability. Malaria and similar diseases aren’t associated with the Cape but tuberculosis (TB) is the most important communicable disease in the region, with the prevalence increasing sharply in recent years due to the HIV/AIDS incidence. A report into the vulnerability of the Cape to climate change, released by provincial government in mid-2005, said that because TB is linked to the standard of living conditions and climatic conditions, this association will have to be scrutinised more closely in future. Extreme events such as floods, also expected to increase in the region, will seriously impact poorer communities living on the Cape Flats particularly as sewage and storm water systems are compromised by flood water. This could lead to outbreaks of water-borne diseases associated with diarrhoea. Food security is expected to be stressed by the increase in drought and flood events. As is so often the case in times of famine, it is not a complete lack of food which leads to starvation and death, but a lack of money to buy increasingly expensive food. Once again, it is the poor who suffer most in times of food shortage. Should food supplies drop, malnutrition will leave these communities more vulnerable to illness and the opportunistic infections associated with HIV/AIDS. The provincial report admits that it is 'not clear at present what health impacts a change in temperature would have in the Western Cape' but does list the above issues as ones which could impact the region as the Cape warms and dries and experiences increased extreme weather events. When it comes, the impact will be counted in lost work days and cost of treatment. Ultimately, though, it will be measured in the loss of human life not only to the economy, but also to the families of those left behind. As Nature again points out: given the bulk of the pollution causing this fallout in vulnerable countries such as Africa originates in developed countries so many thousands of kilometres away, climate change is a 'global ethical challenge'. *Last month’s column Pay up for flooding my vineyard! said that 14 000 deaths were attributed to the heat wave. Both figures originated in Nature but from different papers.