Climate change due to global warming

The increase in carbon dioxide and other pollutants in the atmosphere due to the burning of fossil fuels (coal, petrol, etc.) has led to an increase in global temperature. Although the temperature increase is comparatively small, it has begun to have a major effect on the climate, with a disruption of weather systems and a raising of the sea level. This has been most marked on a system of currents off the west coast of South America known as the El Nino southern oscillation. Climatic systems are reversed or severely disrupted, with heavy rains and flooding when no rain is normally expected and drought conditions when there should normally be rain. Countries in South America, Southeast Asia and Oceania are the most affected, but its effects are felt all over the world. Even without El Nino, there has been an increase in the frequency and severity of storms in many parts of the world.

Increase in temperature has the potential to expand the range of infections that are normally constrained by temperature, for example, malaria. This has led to speculation that malaria could become a problem in the developed countries of Europe and North America where it occurred in former times. However, this is unlikely as good preventive measures are able to keep the disease from spreading even if the malarial mosquito re-establishes itself. A good example is Australia where much of the country lies within the tropical region, the main malaria vector Anopheles farauti (the same as Papua New Guinea and Solomon Islands) is present, yet control methods have eradicated the parasite and continued surveillance has prevented it from being re-introduced.

A more serious problem is in areas of highlands within tropical countries such as East Africa and South America. At a certain altitude where the lower temperature prevents the mosquito and parasite from developing, malaria is not found, but

Fig. 1.7. Mean monthly measles cases, 1977-1981, Mbeya region, Tanzania.


Fig. 1.7. Mean monthly measles cases, 1977-1981, Mbeya region, Tanzania.

evidence from Ethiopia and Kenya has shown that this level is already rising. Malaria is now found at higher altitudes with the rate of ascent linked to the rise in temperature. There is also a greater risk of epidemic malaria with the wider fluctuations of temperature that have resulted and the number of people who have no immunity. Other diseases transmitted by mosquitoes like dengue and Japanese encephalitis, and other arboviruses, such as Rift Valley fever, are likely to increase.

Effects will be most felt at the extremes of the world, i.e. the tropics and the Arctic and Antarctic regions. If ocean levels rise, then small island nations will be threatened by a reduction in land area on which to live and grow their crops and salinity will intrude into freshwater aquifers. Thirteen of the 20 major conurbations are at sea level and the population at risk from storm surges could rise from 45 to 90 million people. Countries at greatest risk are Bangladesh, China, Egypt and the small island nations of the Pacific, Caribbean and Indian Oceans. At the other extreme, a rise in temperature could damage the permafrost, upsetting the balance of nature and the livelihood of the indigenous people who live in these parts of the world. The increase in carbon dioxide will result in preferential conditions for tree growth and the development of forests, which would be beneficial in the long run, but the animals that live in these lands might not be able to adjust to the rate of change and become extinct.

While most of the concern of increase in disease due to global warming has been expressed in the Western world, it is more likely that most of the effects will be concentrated in the poorer regions of the world, with an increase in vector-borne and diar-rhoeal diseases, malnutrition and natural disasters.

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