Climate Change Information Sheet 14
Human health
- Climate change will cause direct health effects . . . Global warming is expected to lead to more cardiovascular, respiratory, and other disease. Injuries, psychological disorders, and deaths would result from a greater intensity and duration of heat waves and perhaps of floods, storms, and other extreme climate events. While warmer temperatures in colder climates should reduce cold-related deaths, such positive effects are not likely to offset the negative ones.
- . . . but indirect effects may be more important in the longer term. Climate change is expected to disturb ecological systems and natural resources, interfere with sanitation and other infrastructure, and cause social and economic dislocations. These trends will expose more people to diseases transmitted by insects, water, and other "vectors". They could also promote infectious diseases such as diarrhea, malnutrition and hunger, and asthma and other allergic disorders.
- Warmer temperatures would enable insects and other disease carriers to expand their range. Organisms such as malarial mosquitoes and schistosome-spreading snails will be well-positioned to spread to higher latitudes and higher altitudes. For example, around 300 million new malaria infections now occur every year, resulting in two million deaths. Approximately 45% of the world's population presently lives in the climate zone where mosquitoes transmit malaria; models predict that this will increase to about 60% by the latter half of the next century. Most of the 50 to 80 million additional annual cases resulting from climate change would occur in tropical and subtropical zones, those temperate zones currently at the margins of infected areas, and areas where people are less well protected.
- Food- and water-related diseases will also increase. Warmer temperatures, reduced water supplies, and proliferating microorganisms would lead to a higher incidence of cholera, salmonellosis, and other such infections. For example, cholera bacteria can survive by sheltering beneath the mucus outer coat of various algae and zooplankton; warmer water may increase algal blooms, helping Vibrio cholerae to multiply and perhaps even promoting the emergence of new genetic strains.
- There is a long list of other potential health effects. Local reductions in food production could increase malnutrition and hunger, with long-term health consequences, particularly for children. Asthma, allergic disorders, and cardio-respiratory diseases could result from climate-induced changes in the formation and persistence of pollens, spores, and certain pollutants. Changes in the production of both aquatic pathogens and biotoxins may jeopardize the safety of seafood.
- Assessing potential health effects involves many uncertainties. Researchers must consider not only future scenarios of climate change but many other variables as well. These include future environmental conditions, such as water purity, and trends in socio-economic conditions such as nutrition, immunization, population density, and access to health care. Nevertheless, despite these complexities researchers do have a high confidence in some of their findings.
- Many health impacts will pose novel questions for public-health science. Simple explanations such as local exposure to environmental contaminants will not suffice. Instead, many problems will result from the indirect and often delayed effects of disturbances to ecosystems.
- Poorer communities will be more vulnerable than rich ones. However, richer countries will also be increasingly vulnerable as their populations age.
- Health risks can be addressed through various adaptation strategies. The lack of resources will be a constraint in many regions, but negative health effects can be minimized through improved medical care services (especially for infectious diseases), health surveillance and sanitation programmes, environmental management, disaster preparedness, improved water and pollution control, public education directed at personal behavior, professional and research training, and protective technologies (such as housing improvements, air conditioning, water purification, and vaccination).
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