How Will Global Warming Affect Human Health?
Certain threats to human health loom larger with rising temperatures. Extremely hot temperatures can cause heat illnesses and loss of life. Several vector borne diseases only occur in warm areas, and an increase in temperature could mean a spread of these diseases to larger areas. Also, warm temperatures can increase levels of air pollutants, including ozone, which can harm human health.
The most direct way that a rise in global mean temperature will affect human health is through a more frequent occurrence of heat waves. Heat can seriously harm or even kill during a heat wave. Extremely high temperatures push the human body beyond its capacity to cool itself through perspiration. Usually, the body perspires and is cooled through the evaporation of that perspiration. In conditions with extremely high temperatures and humidity levels, evaporation slows and the body has to work harder to cool itself. The elderly, the young, the overweight, and the infirm are vulnerable to heat stroke, as are people who have been overexposed to the heat, or have over-exercised for their age and physical condition. Men are more susceptible to heat illnesses than women, because they sweat more and dehydrate more quickly. The problem is exacerbated in urban areas because asphalt, concrete, and other manmade materials absorb a lot of light and reradiate it as infrared radiation, which raises the temperature of the air. In a normal year, about 175 Americans die from extreme heat related illnesses, but that number could rise tremendously in response to global warming. Studies based on heat wave mortality statistics estimate that in Atlanta, even a warming of two degrees would increase the number of heat-related deaths from 78 today to anywhere from 96 to 247 people a year. Increased temperatures also effect people psychologically. Violent crimes and spousal abuse occur more in summer than winter, in hot cities than in cooler cities, and on hotter days than on cooler days. Between 1980 and 1982 in Houston, murders and rapes were more common on days over 91 degrees Farenheit. In laboratory experiments, people working in a hot room react to provocation with greater hostility.
Global warming may increase the risk of some infectious diseases, like malaria, dengue fever, yellow fever, and encephalitis. These diseases are spread by mosquitoes and other insects, and could become more common if a rise in temperature allows those insects to live farther north. Also, the increase in rainfall that is likely to occur with an increase in global temperature would serve to help increase the reproduction of the vectors. In February 1999, Britain's Institute of Animal Health linked outbreaks of the lethal horse fever virus in Africa to the El Nino phenomenon. The warming and increase in rainfall in Africa caused by El Nino led to many more horses...