Global Warming

            
             Global warming is an increase in the average temperature of the earth's surface. As global warming increases, we can expect major changes in climate, water level, agricultural areas, and greenhouse gases. Since the late 1800's, the average temperature has increased about 0.5 to 1.5 Fahrenheit degrees. Scientist disagrees about the causes and potential impact of this warming trend. Global warming affects many aspects of the environment, including sea levels, coastlines, agriculture, forestry, and wildlife. Continued global warming could have a beneficial impact in some areas and a harmful impact in others. For example, people could begin to farm in regions where it is currently too cold. At the same time, global warming could cause sea levels to rise and thereby increase the threat of flooding in low-lying costal areas, many of which are densely populated.
             To determine the impact of global warming, scientists must consider the rate of climate change. Many experts estimate that due to human activities the average surface temperature will rise between 3 and 8 Fahrenheit degrees by the year 2100. But even a warming of 2-Fahrenheit degrees in a century would be several times faster than the typical natural rate. A rapid and large-scale climate change could severely harm the earth's eco system. For example such a change could make it difficult for many species to survive in the regions they now inhabit. Some could be forced to migrate, while others could become extinct. .
             Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases: Carbon dioxide is released to the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal), wood and wood products are burned.