Global Warming Essay

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1.1 What is Global warming?

What is global warming? Global warming is an increase in the Earth's average atmospheric temperature that causes corresponding changes in climate. This results from an increase greenhouse effect.

A panel convened by the U.S National Research Council, (the USA’s premier science policy body), in June 2006 voiced a "high level of confidence" that Earth is the hottest it has been in at least 400 years, and possibly even the last 2,000 years. Studies indicate that the average global surface temperature has increased by approximately 0.5-1.0°F (0.3-0.6°C) over the last century. This is the largest increase in surface temperature in the last 1,000 years and scientists are predicting an even greater increase over this century. This warming is largely attributed to the increase of greenhouse gases (primarily carbon dioxide and methane) in the Earth's upper atmosphere caused by human burning of fossil fuels, industrial, farming, and deforestation activities including. 

www.solar-center.stanford.edu/sun-on-earth/glob-warm.html

1.2 Green house effect

There are two meanings of the term "greenhouse effect". There is a "natural" greenhouse effect that keeps the Earth's climate warm and habitable. There is also the "man-made" greenhouse effect, which is the enhancement of Earth's natural greenhouse effect by the addition of greenhouse gases from the burning of fossil fuels (mainly petroleum, coal, and natural gas). In order to understand how the greenhouse effect operates, we need to first understand . Greenhouse gases trap some of the infrared radiation that escapes from the Earth, making the Earth warmer that it would otherwise be. You can think of greenhouse gases as sort of a "blanket" for infrared radiation-- it keeps the lower layers of the atmosphere warmer, and the upper layers colder, than if the greenhouse gases were not there.

About 80-90% of the Earth's natural greenhouse effect is due to water vapour, a strong greenhouse gas. The remainder is due to carbon dioxide, methane, and a few other minor gases.
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It is the carbon dioxide concentration that is increasing, due to the burning of fossil fuels (as well as from some rainforest burning). This is the man-made portion of the greenhouse effect, and it is believed by many scientists to be responsible for the
 of the last 150 years. Also, the concentration of methane, although small, has also increased in recent decades. The reasons for this increase, though, are uncertain.


2 The impact of Global warming

The impacts of  are already occurring in the Arctic with temperatures rising twice as fast as they are elsewhere in the world. This warming trend could greatly affect sea level rise, ocean circulation systems and salinity, and change marine habitats threatening many species with extinction.

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Scientist’s project that melting of glaciers and land based arctic ice could raise sea level by as much as 3 feet by 2100, threatening low-lying coastal areas from the Gulf of Mexico and Florida to Bangladesh. Melting of the Greenland Ice Sheet could cause sea level to rise by as much as 23 feet. There are signs that this process has begun, although total melting is likely to take up to 1,000 years.

Polar bears could face extinction this century if the Arctic continues to melt at its present rate. The sea ice around the North Pole on which bears ...

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