Weather wise

In their recent report The Regional Impacts of Climate Change (CUP, pounds 24.95), the Inter-Governmental Panel on Climate Change paints a grim picture of the potential effects of global warming. While frequently stressing that all predictions depend on the accuracy of unproven computer models, the writers produce a convincing analysis of the damaging changes we may all face if the models are correct.

In one respect at least, the IPCC report is already being vindicated. "The direct and indirect impacts of climate change on human health," they write, "do constitute a hazard to human population health, especially in the tropics and sub-tropics; these impacts have considerable potential to cause significant loss of life." Yesterday World Health Organisation workers in Kenya reported just such an outbreak of climate- related disease, but the overall message was far from gloomy.

In north-east Kenya and southern Somalia, 400 lives have been lost this year to diseases brought on by flooding caused by El Nino. Half of these have been related to Rift Valley fever, which can cause fatal haemorrhaging. The mechanism is relatively simple: floods create the breeding grounds for mosquitoes, which transmit the disease to humans and livestock. People can also become infected from the slaughter of infected animals.

The good news, however, is that accurate weather forecasting may enable such outbreaks to be contained. "There is increasing evidence that these outbreaks can be predicted," said Mike Ryan, who heads a team of 15 WHO experts investigating the present outbreak. While experiments are continuing in the search for a human vaccine against Rift Valley fever, a vaccine for animals is already available.

Scientists are now examining weather patterns at the time of historical outbreaks of the disease to see if correlations can be established that would enable future outbreaks to be predicted. Animals could then be rapidly immunised and the spread of the disease curbed. Last year, Dr Ryan said, satellite data was used to predict an outbreak of malaria in Colombia.

According to a report in November, doctors in Peru blamed El Nino for high temperatures that led to an outbreak of dehydration and diarrhoea among infants. In early December, malaria cases in Venezuela increased by an average of 37 per cent in the years following an El Nino event. At the end of the same month, Thailand reported a doubling on the previous year of the number of cases of dengue fever, which was also blamed on the stagnant waters left by El Nino. If improved weather forecasting can lead to better preparedness for such outbreaks, then the news from the WHO is very encouraging.