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Q 1: Carbon cycles through the ecosystem between the atmosphere, organisms (such as producers, herbivores, and carnivores), and decomposers. This natural cycle maintains a somewhat constant level of carbon in the atmosphere. The burning of fossil fuels releases carbon into the cycle that has been trapped inside the earth. How does this affect the cycle and what problems can this cause?

In the natural carbon cycle, there are two main processes which occur: photosynthesis and metabolism.

During photosynthesis, plants use carbon dioxide and produce oxygen. During metabolism oxygen is used and carbon dioxide is a product.

Humans impact the carbon cycle during the combustion of any type of fossil fuel, which may include oil, coal, or natural gas. Fossil Fuels were formed very long ago from plant or animal remains that were buried, compressed, and transformed into oil, coal, or natural gas. The carbon is said to be "fixed" in place and is essentially locked out of the natural carbon cycle. Humans intervene during by burning the fossil fuels. During combustion in the presence of air (oxygen), carbon dioxide and water molecules are released into the atmosphere.

The question becomes as to what happens to this extra carbon dioxide that is released into the atmosphere. This is the subject of considerable debate and about it possible effect in enhancing the greenhouse effect which may than result in global warming.

Human activities are making the blanket "thicker" -- the natural levels of these gases are being supplemented by emissions of carbon dioxide from the burning of coal, oil, and natural gas; by additional methane and nitrous oxide produced by farming activities and changes in land use; and by several long-lived industrial gases that do not occur naturally.

These changes are happening at unprecedented speed. If emissions continue to grow at current rates, it is almost certain that atmospheric levels of carbon dioxide will double from pre-industrial levels during the 21st century. It is possible they will triple.

The result, known as the "enhanced greenhouse effect," is a warming of the earth's surface and lower atmosphere. The IPCC assesses with very high confidence that the globally averaged net effect of human activities since 1750 has been one of warming. The 'best case' computer climate models estimate that the average global temperature will rise by 1.8° C to 4.0° C by the year 2100. A temperature increase of 0.74° C occurred last century and for the next two decades, a warming of about 0.2° C per decade is projected should greenhouse gas emissions continue to rise at their current pace and are allowed to double from their pre-industrial level.

A rise in temperature will be accompanied by changes in climate -- in such things as cloud cover, precipitation, wind patterns, and the duration of seasons. In its Fourth Assessment Report, the IPCC projects that heat waves and heavy precipitation events are very likely to increase in frequency in the 21st century. In a world that is crowded and under stress, millions of people depend on ...
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