Global Warming
The warming of the Earth has been the subject of intense debate and concern for many countries and their citizens. The warming has been particularly strong during the last 20-25 years and has been accompanied by retreating glaciers,thinning arctic ice,rising sea levels,lengthening of growing seasons for some,and earlier arrival of migratory birds. In addition ,several other data support that conclusion.
Part of the debate over global warming centres on disparities between the surface temperature and upper air temperature. While the Earth's temperature has risen ,data collected by sattelites and various other instruments.
Concentrations of greenhouse gases will accelerate and conservative assumptions about how climate will react to that, computer models suggest that average global surface temperatures will rise between 2.5 to 10.4 degree fahrenheit and 1.4 and 5.8 degree celsius by the end of this century.
Projecting how the world's climate will change in the future requires estimating the amount of greenhouse gases by burning fossil fuels and other human activities. These gases often remain in the atmosphere for many years, trapping radiation that would naturally escape into the atmosphere. Several components of climate change indentified that are highly uncertain and make it difficult to predict future changes.
Global warming in the last 50 years is likely the result of increases in greenhouse gases, which accurately reflects the current thinking of the scientific community,the committee said.
However, it also cautioned that uncertainties about this conclusion remain because of the level of natural variability inherent in the climate on time scales, and the degree of confidence that can be placed on estimates of temperatures going back thousands of years based on evidence from tree rings or ice cores.
Almost all the major greenhouse gases with the (CFCs) have both natural and human induced sources. For example,carbon dioxide is not only formed by the decay in plant matter,but also by the burning of coal,oil,natural gas, and wood. And cattle, coal mining, using land fills, and handling natural gas. Both carbon dioxide and methane are most abundant in earths atmosphere now than at any time during the past years, report says. In addition, the other greenhouse gases combined contribute to climate changes approximately equal to that of carbon dioxide.
The use of CFCs which were employed in a variety of industrial applications including refrigeration, air conditioning, and aerosols.
climate change and its consequeces are likely to have strong regional effects, but regional projection can vary substantially from climate model to climate model.
Some models predict increased tendency of drought in some regions and higher rainfalls on others. In near term , agriculture and forestry may benefit, but hotter and drier conditions increase the potential for crop distributions to change. Areas around the country that already have water shortages or water quality problems could see these problems exacerbated.
The impact of climate change on human health is the subject of intense Debate.