The skill to safely navigate the hazards of power and the powerful |
2 0 0 0 T i m e s . c o m |
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The Environment |
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What Causes Global Warming? Answer: Scientists have determined that a number of human activities are contributing to global warming by adding excessive amounts of greenhouse gases to the atmosphere. Greenhouse gases such as carbon dioxide accummulate in the atmosphere and trap heat that normally would exit into outer space. Greenhouse Gases and Global Warming While many greenhouse gases occur naturally and are needed to create the greenhouse effect that keeps the Earth warm enough to support life, human use of fossil fuels is the main source of excess greenhouse gases. By driving cars, using electricity from coal-fired power plants, or heating our homes with oil or natural gas, we release carbon dioxide and other heat-trapping gases into the atmosphere. Deforestation is another significant source of greenhouse gases, because fewer trees means less carbon dioxide conversion to oxygen. During the 150 years of the industrial age, the atmospheric concentration of carbon dioxide has increased by 31 percent. Over the same period, the level of atmospheric methane has risen by 151 percent, mostly from agricultural activities such as raising cattle and growing rice. The Consequences of Global Warming As the concentration of greenhouse gases grows, more heat is trapped in the atmosphere and less escapes back into space. This increase in trapped heat changes the climate and alters weather patterns, which may hasten species extinction, influence the length of seasons, cause coastal flooding, and lead to more frequent and severe storms.
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Question: What are Greenhouse Gases? Answer: Many greenhouse gases occur naturally, such as water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Others such as hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) result exclusively from human industrial processes. Human Activities and Greenhouse Gases Human activities also add significantly to the level of naturally occurring greenhouse gases: Carbon dioxide is released into the atmosphere by the burning of solid waste, wood and wood products, and fossil fuels (oil, natural gas, and coal). Nitrous oxide emissions occur during various agricultural and industrial processes, and when solid waste or fossil fuels are burned. Methane is emitted when organic waste decomposes, whether in landfills or in connection with livestock farming. Methane emissions also occur during the production and transport of fossil fuels. The Properties of Greenhouse Gases Greenhouse gases vary in their ability to absorb and hold heat in the atmosphere, a phenomenon known as the "greenhouse effect." HFCs and PFCs are the most heat-absorbent, but there are also wide differences between naturally occurring gases. For example, nitrous oxide absorbs 270 times more heat per molecule than carbon dioxide, and methane absorbs 21 times more heat per molecule than carbon dioxide. |
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Answer: Throughout most of human history, and certainly before human beings emerged as a dominant species throughout the world, all climate changes were the direct result of natural forces. Industrial Age Accelerates Global Warming That changed with the start of the Industrial Revolution, when new agricultural and industrial practices began to alter the global climate and environment. Before that time, human activity didn’t release many greenhouse gases, but population growth, deforestation, factory farming, and the widespread use of fossil fuels are creating an excess of greenhouse gases in the atmosphere and contributing to global warming. Science Links Global Warming to Human Activity In February 2007, a report by the Intergovernmental Panel on Climate Change (IPCC), representing the work of 2,500 scientists from more than 130 countries, stated that human activity "very likely" has been the primary cause of global warming since 1950. (In science, nothing is ever claimed to be "certain" or absolute, which leaves open the possibility of further research and discovery, but the term “very likely” indicates more than 90 percent certainty and is considered virtual confirmation.) The IPCC report also said that human activity has been a major contributor to climate change since the start of the Industrial in the mid-1700s.
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