The Department of Health and the Health Protection Agency have recently published an update to their seminal 2002 report Health Effects of Climate Change in the UK.

By the end of this century, climate change models predict an increase in the mean annual temperature in the UK of 2.5-3C. Average air temperatures for the area between Preston, Bristol and London have been recorded monthly since 1659. Apart from the 'little ice age' around 1690, average temperatures wobbled between 9 and 9.5C up to the 1950s. Since then they have increased continuously to reach 10.5C (see first chart).

The rise in temperature is only part of the story; extremes are also becoming more common. On 10 August 2003 maximum night-time temperatures exceeding 37C were recorded in a number of places; summer 2003 saw 14,000 heat-related deaths in France and the fourth overall hottest summer since the 17th century. It was the hottest in Europe since 1500.

While scientists would welcome being proved wrong, the consensus is that climate change has been happening for some time and human activities significantly contribute.

Taking the latest climate change predictions and assessing potential impact on health in the UK adds another layer of predictive trickiness. The DoH-commissioned report summarises experts' best guesses and collated modelling research under various weather conditions.

For some weather changes, such as higher average wind speeds, the impact on health is thought to be negligible. For others, like rising sea levels, probabilities increase for higher frequencies of floods, and catastrophic events such as a breach of the Thames tidal floodplain.

Warmer weather, especially in the South East, could encourage an increase in diseases such as malaria. Higher temperatures could lead to higher levels of food contamination and disease but these could be dealt with through stricter hygiene. The same qualifier goes for water-borne diseases. However, uncertainty about the estimates arises from whether efforts are made to prevent such problems.

As for the direct health effects of increased temperatures, there is evidence of an increased tolerance. Nevertheless, with heat-related deaths increasing rapidly as temperatures exceed 27C, the climate report suggests there is a one in four chance of a nine-day heat wave each year over the period 2007 to 2017 (see second chart). This could kill around 6,400 people each year.

Professor John Appleby is chief economist at the King's Fund.