Climate means the average pattern in which weather varies in time. The climate of region depends on the presence or absence of water, the reflection of solar radiation or albedo, the ability to transfer water to the atmosphere (evaporation), the capacity to store heat, topography and texture of the region.
Although they constitute only a fraction of the total land area of the earth, metropolitan areas emits the bulk of all air pollutants. These air pollutants influence temperature, visibility and precipitation as well as other climatic elements.
The average temperature in many regions has been increasing in recent decades. The global average surface temperature has increased by 0.6° C – 0.20° C over the last century. Globally, 1998 was the warmest year and the 1990s the warmest decade on record. Many countries have experienced increases in rainfall, particularly in the countries situated in the mid-to high- latitudes.
In some regions, such as parts of Asia and Africa, the frequency and intensity of droughts have been observed to increase in recent decades. Episodes of El Nino, which creates great storms, have been more frequent, persistent and intense since the mid-1970s compared with the previous 100 years. All these are signs that the Earth is ailing. Its climate is changing, making it more difficult for mankind to survive. The earth is losing its equilibrium due to the imbalances created by human activities.
Projections of future climate change are derived from a series of experiments made by computer based global climate models. These are calculated based on factors like future population growth and energy use. Climatologists of the intergovernmental panel on climate change (IPCC) have reviewed the results of several experiments in order to estimate changes in climate in the course of this century.
These studies have shown that in the near future the global mean surface temperature will rise by 1.4°C – 5.8° C. this ‘warming’ will be greatest over land areas, and at high latitudes. The projected rate extreme is likely to increase, leading to floods or drought. There will be fewer cold spells but more heat waves. The frequency and intensity of the El Nino is likely to increase.
The global mean sea level is projected to rise by 9.88 cm by the year 2100. More than half of the world’s population now lives within 60 km of the sea. They are likely to be seriously impacted by the ingress of salt water and by the rising sea. Some of the most vulnerable regions are the Nile delta in Egypt, the Ganges- Brahmaputra delta in Bangladesh, and many small islands including the Marshall islands and the Maldives, (WHO, 2001).
Human societies will be seriously affected by extremes of climate such as droughts and floods. A changing climate would bring about changes in the frequency and/or intensity of these extremes. This is also a fundamental concern for human health. To a large extent, public health depends on safe drinking water, sufficient food, secure shelter, and good social conditions. All these factors are affected by climate change.
Freshwater supplies may be seriously affected, reducing the availability of clean water for drinking and washing during drought as well as floods. Water can be contaminated and sewage systems may be damaged. The risk of spread of infectious diseases such as diarrheal also indirectly through an increase in pests and plant or animal diseases.
The local reduction in food production would lead to starvation and malnutrition with land-term health consequences, especially for children. Food and water shortages may lead to conflicts in vulnerable regions. Climate change related impacts on human health could lead to displacement of a large number of people, creating environmental refugees and lead to further health issues.
Changes in climate may affect the distribution of vector species (e.g., mosquitoes) which, in turn, will increase the spread of disease, such as material and filariasis, to new areas which lack a strong public health infrastructure. The seasonal transmission and distribution of many diseases that are transmitted by mosquitoes (dengue, yellow fever) and by ticks (Lyme disease, tick-borne encephalitis) may spread due to climate change.
The United Nations Framework Convention on Climate Change (UNFCCC) defines climatic change as a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time period.
Projections of future climate change are derived from a series of experiments made by computer based global climate models. These are calculated based on factors like future population growth and energy use. Climatologists of the Intergovernmental Panel on Climate Change (IPCC) have reviewed the result of several experiments in order to estimate changes in climate in the course of this century. These studies have shown that in the near future the global mean surface temperature will rise by 1.4° – 5.8°C this ‘warming’ will be greatest over land areas, and at high latitudes.
The projected rate of warming is greater than has occurred in the last 10,000 years. The frequency of weather extremes is likely to increase, leading to floods or drought. There will be fewer cold spells but more heat waves. The frequency and intensity of the El Nino is likely to increase.