Warmer and sicker? Global warming and human healthThis topic is sponsored by the Australian Greenhouse Office. Continued warming of the planet could have significant implications for human health. Coping with extreme heatwaves will be just one of our concerns. Key text Key textGlobal warming will have many impacts on human healthIn August 2003, Europe suffered its worst heatwave in recent memory. In France, temperatures peaked at about 40°C; unprepared for that kind of heat, many people – mostly the sick and elderly – succumbed. In all, nearly 15,000 deaths in France that summer were attributed to the high temperatures; across Europe, the scorching weather may have claimed as many as 35,000 lives. According to the bulk of scientific opinion, the world is getting warmer. It is difficult, if not impossible, to prove the causes of this warming, but many scientists are convinced that increasing concentrations of greenhouse gases in the atmosphere are at least partly to blame. How might the climate change? Scientists use computer-based models to predict the effects on global climate of different levels of greenhouse gases in the atmosphere. According to the most recent projections of the Intergovernmental Panel on Climate Change (IPCC), the global mean temperature could increase by 1.4°C to 5.8°C between 1990 and 2100. The climatic effects of such a temperature increase might include:
In Australia the climate is expected to become significantly warmer: by 2070 the annual average temperature is predicted to increase by 1°C to 6°C over most of Australia. The number of extreme rainfall events – such as those leading to flooding – is also expected to increase, even though most of the country is anticipated to become drier overall in the 21st century. Heatwaves and cold snaps Perhaps the most obvious impact of global warming will be the direct effects: a warmer planet will experience more extreme heatwaves. As seen in Europe in 2003, heatwaves often lead to an increase in the number of human deaths, particularly in temperate countries where people are often not accustomed to very hot weather and where houses and other infrastructure are not designed to cope with it. The sick and elderly are most vulnerable because their bodies are less able to increase cardiac output and sweat function for cooling purposes; they are often less able to afford cooling technologies. It is difficult to predict the future effect on mortality levels, because as heatwaves become more frequent we can expect societies to adjust – technologically, behaviourally and physiologically. Technological adaptations such as the installation of effective air-conditioners and the construction of heat-minimising houses will happen more quickly among the rich, so heatwaves are likely to have a disproportionate effect in less-developed countries and in the poorer segments of rich societies. In countries that currently experience extremely cold weather in winter, an increase in the mortality rate in summer might be offset by a decrease in winter mortality. Northern countries with severe winters have a higher mortality rate in winter because more sick and elderly people succumb in cold weather and because blizzards and extreme cold create dangerous conditions in which accidental deaths are more likely. Winters will tend to be milder under global warming, with the likely effect that winter death rates will decline. Without measures to mitigate the effects of extreme heat, and with an increase in the proportion of older people in the population, we might therefore expect higher death tolls in Australia's future heatwaves. It is estimated that there are currently about 1100 heat-related deaths per year. Extreme events and disasters Most computer models generated by scientists indicate that the future climate will be more variable than in the past, and that droughts and floods will be more severe. Some of the health effects of weather-related disasters, in addition to the immediate death and injury to people and damage to property, include:
Australia's climate is naturally variable, although generally arid. In such a country, the implications of an even greater variation in rainfall is likely to be profound. Apart from the ecological and agricultural impacts, the availability of water may be reduced, with implications for human health. More frequent drought conditions would increase the risk of bushfires, which can kill people, release large quantities of particulate matter that can cause respiratory problems, and degrade water catchments. Infectious diseases Many infectious diseases are dependent on vector organisms, which are sensitive to environmental factors and therefore will be affected by global warming. Biological modelling under various climate scenarios suggests a widening of the potential transmission zone of some disease-causing pathogens and their vectors, such as mosquitoes (Box 1: Mosquito-borne disease). Food- and water-borne diseases are also susceptible to climate change. Already, Australians suffer an estimated 4.6 million cases of diarrhoea or gastroenteritis each year, often caused by food contaminated with bacteria, parasites and (to a lesser extent) fungi and viruses. Food-poisoning bacteria grow best when the ambient temperature is in the range 35-37°C. Scientists speculate that if temperatures rise under global warming, the incidence of diseases caused by food-poisoning and by the contamination of drinking (and swimming) water could increase dramatically. Rising sea levels Scientists predict that sea levels will rise as the global temperature rises, due to the melting of land-based ice in the polar regions and glaciers, and the thermal expansion of the oceans. According to the most recent projections, sea levels could rise between 9 and 88 centimetres by the year 2100. A rise of this magnitude would have disastrous consequences for people living on low-lying islands, such as the Maldives group in the Indian Ocean and many South Pacific islands. Higher sea levels lead to coastal flooding and an increase in the frequency of extreme high water levels from storm surges. Related problems are the contamination of coastal freshwater supplies with encroaching sea water, and the degradation of fishing and agricultural areas. The number of Australian fatalities from coastal flooding and storm surges has historically been low. It is currently estimated that 250 people each year experience coastal flooding due to storm surges, but this number could double by 2050. For the Pacific region as a whole, however, the number of people exposed to coastal flooding could be between 60,000 and 90,000 in an average year, a 50-fold increase on today's estimates. Warmer and sicker? Considerable uncertainty remains about how the climate may change and how such changes might affect human health. It seems likely, however, that people living in tropical and sub-tropical areas will be most affected. Affluent countries and social groups will be best able to adapt to climate change by reducing the impacts of natural disasters such as flooding, fire and drought, by maintaining high-quality health and emergency infrastructures, and by installing technologies that help ward off the worst climatic effects. Neither uncertainty nor complacency should be allowed to prevent action to reduce greenhouse gas emissions. The risk to human (and ecological) well-being is too great, and prevention will be far better – and easier – than cure. Related Nova topics: Getting into hot water – global warming and rising sea levels Enhanced greenhouse effect – a hot international topic
Malaria kills between one and two million people every year, mainly in tropical Africa, and debilitates up to 400 million others. This disease is caused by protozoans from the genus Plasmodium, which are transmitted from person to person by mosquitoes from the Anopheles genus. Scientists believe that climate is the major determinant of malaria distribution in Africa – both the vector and the protozoa prefer warm, humid conditions. Mosquito control measures are largely responsible for limiting its distribution in other regions. Malaria was once endemic in parts of northern Australia, but was eradicated by control measures and changes to water supply practices. Only a dozen or so locally acquired cases have been reported since 1962. Modelling suggests that climatic conditions are currently suitable for the survival of both the protozoa and its mosquito vector in the very north of the continent. Under a warmer and wetter climate-change scenario, the malaria-receptive zone could spread down the coast to southern Queensland by 2050 – including to towns such as Rockhampton, Gladstone and Bundaberg – and into the coastal hinterland. Under a warmer and drier scenario, the disease could still be transmitted in southern Queensland, but would be more limited to the coastal zone and islands. A report published by the Australian Australian Government Department of Health and Ageing in 2003 concluded that malaria is unlikely to constitute a major direct threat to human health in Australia under climate change 'as long as a high priority is placed on prevention via the maintenance and extension of public health and local government infrastructure'. The authors predict a similar increase in the potential distribution of dengue fever in Australia, although dengue would probably be a greater threat to public health. This is because dengue's mosquito vector is a morning and evening biter and can breed in urban environments, increasing the risk of exposure, and because no treatments are available to reduce the period in which victims are infectious. Related site
Activities
Further readingAustralasian Science Jan/Feb 2008, page 10 Climate change will make you sick Reports on the problems of climate change on the health of Australians.
June 2007, pages 34-35 Climate change to hit health (by Tony McMichael) Summarises the health challenges associated with global warming in Australia.
July 2003, page 9 Health risks of greenhouse quantified Summarises a report by leading Australian research institutions that quantifies the health risks this region will experience as the result of global warming.
Cosmos October-November 2006, pages 34-35 Fever pitch (by Mark Juddery) Reports that as the world warms, mosquitoes will spread more widely, spreading diseases.
New Scientist 27 February 2008, page 16 Global warming twice as lethal as previously assumed Examines the impact of carbon dioxide levels on death rates.
29 November 2006 Can flu viruses survive winter in frozen lakes? (by Catherine Brahic) Looks at the possibility of viruses frozen in Siberian lakes being released as a result of global warming.
19 June 2004, pages 8-9 Climate blamed for upsurge in disease (by James Randerson) Looks at the relationship between emerging and resurgent diseases and climate change.
30 November 2002, pages 26-29 Plague of plenty (by Graham Lawton) Looks at how rising CO2 levels could trigger a pandemic of human malnutrition due to a decrease of micronutrients in food plants.
29 June 2002, page 22 Global warming, global fever (by Mark Schrope) Summarises research that used epidemiological studies and climate model projections to look at the effect of global warming on diseases.
3 November 2001, pages 36-39 Ask the experts (by Sue Armstrong) Looks at how Canada's Inuit are tackling the consequences of climate change.
Scientific American May 2008, pages 68-73 The ethics of climate change: Pay now or pay more later? (by John Broome) Discusses the ethical and economic implications of dealing with climate change.
21 March 2006 Study supports possible connection between climate change and malaria rise (by David Biello) Describes a study indicating that increased outbreaks of malaria in East Africa may be due to global warming.
10 March 2005 New malaria map shows disease more widespread than previously thought (by Sarah Graham) The WHO and other international aid organizations have launched a campaign to halve the incidence of malaria by 2010.
21 February 2002 Research challenges proposed link between malaria growth and global warming (by Kate Wong) Research challenges the idea that global warming has increased the incidence of malaria.
August 2000, pages 36-43 Is global warming harmful to health? (by Paul R. Epstein) Looks at ways in which rising temperatures will affect human health.
Useful sitesClimate change and human health – risks and responses. Summary (World Health Organization) Describes the process of global climate change
and its current and future impacts on human health. It also looks at how
societies can lessen the adverse effects of climate change through a variety
of strategies. The information is easy to understand and covers a wide
range of factors. The document is available in either PDF or HTML versions.
Human health and climate change in Oceania: A risk assessment 2002 (Australian Government Department of Health and Ageing, Australia) Looks at a range of climate change scenarios and the potential health
impacts in Australia, New Zealand and the Pacific Islands.
Australian Medical Association and Australian Conservation Foundation
The health benefits of mitigating global warming in Australia (Climate Action Network Australia) Reviews the literature about the public health impacts of climate change
due to global warming as predicted for Australia in the coming decades.
IRI climate information digest (International Research Institute for Climate Prediction, Columbia University, USA) A monthly summary of recent climate events, impacts and seasonal forecasts.
Click on the calendar to see the previous month's summary. Each monthly
edition has climate impacts on health.
Climate change: Observations and predictions (Hadley Centre for Climate Prediction and Research, UK)
This report attempts to answer three important questions: Is the climate changing? What has caused the climate to change? And how much do we expect the climate to change in future?
Maps and graphics (United Nations Environment Progamme, GRID Arendal)
Provides a wide range of graphics showing the impact of climate change, including changes to the distribution of diseases.
Ecology drives the global distribution of human diseases (Public Library of Science, Biology, USA) Synopsis of a research article looking at factors that determine the
geographic range of human pathogens and the impact of global climate change.
The site contains a link to the original article.
Risk of malaria transmission (The Exploratorium, USA) Provides a map showing an increase in conditions suitable for malaria transmission in Europe and the eastern United States.
Australian Broadcast Corporation (transcripts)
Glossaryendemic. Describes a species (or other unit of classification) that occurs in one particular region in all months of the year, and in all years. For example, the platypus is endemic to southeast Australia, and malaria is endemic to parts of Africa.greenhouse gas. A gas that is transparent to incoming solar radiation and absorbs some of the longer wavelength infrared radiation (heat) that the Earth radiates back. The result is that some of the heat given off by the planet accumulates, making the surface and the lower atmosphere warmer. For more information see The greenhouse effect (CSIRO Atmospheric Research, Australia). global warming. An increase in the average temperature of the Earth's surface. Global warming is one of the consequences of the enhanced greenhouse effect and will cause worldwide changes to climate patterns. Intergovernmental Panel on Climate Change (IPCC). An organisation established in 1988 by the World Meteorological Organization and the United Nations Environment Programme to provide the most widely accepted information available about climate change. The IPCC does not conduct new research or monitor climate-related data. Its mandate is to assess existing data and to produce balanced and objective publications. For more information see Intergovernmental Panel on Climate Change (Switzerland). storm surge. A rise in sea-level accompanying a hurricane or other intense storm. Storm surge height is usually measured as the difference between the observed sea-level height and the normal sea-level height. The main causes of storm surge are wind and reduction in atmospheric pressure. vector. An organism that transmits parasites, viruses or bacteria from one host to another. External sites are not endorsed by the Australian Academy of Science. Page updated May 2004. © Australian Academy of Science |