What is Global Warming?
Global Warming refers to the recent warming of temperatures worldwide. It is implied that the temperature change is influenced by human activities. Geologic evidence indicates that numerous cycles of warming, followed by subsequent cooling have occurred in the past.
The Greenhouse Effect
Certain gases (called greenhouse gases) that are generated by human activities prevent heat from escaping into space, similar to the glass panes of a greenhouse (U.S. EPA website). The greenhouse gases include carbon dioxide, methane, nitrous oxide, and fluorinated gases. During the last 200 years or so the activities of man, including burning fossil fuels, such as coal and oil, and deforestation, have caused the concentrations of greenhouse gases to increase significantly in the atmosphere.
Paleoclimatology is the study of climate taken on the scale of the entire Earth to determine past climatic conditions (Wikipedia). It uses evidence from ice sheets, tree rings, sediment, and rocks to determine past climates.
Some researchers consider atmospheric carbon dioxide concentration an important condition controlling global warming and cooling (Ward, 2007). Increased carbon dioxide concentration promotes global warming, while reduced carbon dioxide leads to global cooling. The Eocene epoch (Geologic Time), 34 to 56 million years ago, was the last time the earth was totally warmed to tropical conditions from pole to pole. Fossil evidence indicates that mass extinctions of species have occurred during each significant period of global warming.
Between intervals of global warming,
paleoclimatology has documented periods of global cooling.
During the most intense of global cooling, the evidence
suggests, the earth has cooled to arctic conditions from pole to pole.
What About the Future?
The current global warming trend will likely continue into the future. A number of scientific analyses indicate, but do not prove, that rising levels of greenhouse gases in the atmosphere are contributing to climate change (Corbett and Dannemiller, 2007). Worldwide changes will likely continue at a slow rate requiring many years. If the trend results in an eventual loss of all ice, a worldwide rise in sea-level is estimated to be on the order of 25 feet (7.6 meters). This would result in flooding the world's coastal cities, much land (including agricultural land), and villages. It is not known if altering man's activities involving the generation of greenhouse gases would change the current trend of global warming.
Some Useful Links
Following are some hyperlinks that can further assist with the evaluation and description of global warming and climate change:
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