|Mean annual Central England Temperature (CET) since the 17th century: full record and the last 44 years. Click to enlarge.|
The UK Department of Health (DH) has released an update to its 2002 report that assessed the effects of climate change on human health.
An important feature of the new report, according to the DH, is the update of the climate change scenarios as the context for assessing the impact on human health. Models used in the new report predict an increase of mean annual temperature in the UK of between 2.5 and 3 degrees Centigrade by the end of the century.
Periods of very cold weather will become less common, but periods of very hot weather (heatwaves) will become more common. Application of the epidemiological concept of ‘attributable risk’ to meteorological data allows us to assess the extent to which human influence on climate has contributed to the risk of a specific weather event. Using this approach, a significant role for human influence can already be identified in, for example, the European summer heatwave of 2003 which contributed to over 14,000 premature deaths in France. Changes in wind and rainfall are less certain but periods of sudden heavy rain seem likely to become more common despite a possible reduction in annual rainfall in some areas. Flooding is an increasing risk.
The predicted risk of severe coastal flooding remains low, but will increase as sea levels rise. Referencing earlier work, the authors estimate that the number of people at a high risk from flooding could rise from 1.5m today to 3.5m by 2100. The report stresses the need for upgraded coastal defenses in East Anglia.
The report concludes that the picture concerning vector-borne diseases (e.g., mosquitoes carrying malaria) is more encouraging than thought before.
Reappraisal of the evidence suggests that outbreaks of malaria in the UK are likely to remain rare, though Health Authorities need to remain alert to the possibility of outbreaks of malaria in other European countries and to the possibility that more effective vectors (different species on mosquito) may arrive in the UK. Rapid response to outbreaks of malaria will reduce the chances of the disease becoming endemic in the UK. Tick-borne disease are likely to become more common in the UK, but this will be more likely to be due to changes in land use and leisure activities than to climate change. The likelihood that Tick-borne encephalitis will become established in the UK is very low.
Warmer summers will likely result in an increase in foodborne diseases, as reflected in the initial report. However, the authors took a new and closer look at the impact of climate change on the supply of drinking water. They identified three problems in that area:
Increased short-duration, high-intensity rainfall events leading to increased numbers of bacteria in surface water;
Increased water temperature leading to an increase in algal blooms in reservoirs; and
A decrease in the efficiency of chemical coagulation: a major method of removal of microbes from drinking water.
Regarding the direct effects of high temperatures on health, the authors note that although summers have become warmer in the UK, no change in heat-related deaths occurred during the period from 1970-2003. They conclude that this suggests that the UK population is capable of adapting to warmer conditions. However:
Predicting severe heatwaves and their effects is difficult, but there is a 1 in 40 chance that by 2012 South-Eastern England will have experienced a severe heatwave that will cause perhaps 3,000 immediate heat-related deaths and 6,350 heat-related deaths. In terms of conventional thinking about risks to health a risk of 1 in 40 is high. Winter deaths will continue to decline as the climate warms.
The report projects that the concentration of ozone is likely to increase, although concentrations of other important pollutants are likely to decline over the next half century. Increased ozone concentration will increase attributable deaths and hospital admissions.
The increases are likely to be significant: with the least constraining assumptions (no threshold of effect assumed) up to about 1,500 extra deaths and hospital admissions per annum might be expected.
Skin cancers are also expected to increase with increased exposure to ultra-violet light.
The report suggests that the National Health Service (NHS) needs to adapt the health and social care infrastructure (hospitals, nursing homes) to be more resilient to the effects of heat, gales and floods; develop local “Heatwave”, “Gale” and “Flood” plans for coping with disasters; and increase awareness of how people can adapt to changes in climate.
That last element is summarized as: “Keep cool, keep clean, keep covered.”