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Unformatted text preview: LeeGlobalWarming:1 DRAFT–still being worked on Global Climate Change History Evidence Likely Causes Projections of Future Climates Consequences The Controversy Dealing with Global Warming Global Warming is a controversial topic. The purpose of this lecture is to provide a background on what scientists know about contemporary global climate change, what seems to be driving it and how educated people who are not professional climate scientists should view the problem. History of the Science We have already discussed the greenhouse effect and how water vapor, carbon dioxide, methane and other substances in the atmosphere affect air temperature by absorbing longwave radiation and emitting their own longwave radiation, which we called counterradiation. Several scientists developed the idea of the greenhouse effect in the Nineteenth Century. Joseph Fourier (1768–1830), a French physicist, determined that Earth’s surface absorbs solar energy, but doesn’t just keep heating up because it disposes of this energy by radiating it’s own energy as infrared radiation. But his calculations suggested that if this is so, Earth should be much colder than it is. He determined that somehow the air was holding in the heat and he came up with the greenhouse analogy that the air acted like the glass roof of a greenhouse. Irish scientist John Tyndall (1820-1893) did some experiments in the 1850s and determined that water vapor, methane and carbon dioxide captured heat energy and could account for the warmth of the air. These are called “greenhouse gasses.” The idea of ice ages was new in the middle of the 1800s and Tyndall was seeing if changes in the atmospheric composition, especially water vapor, could bring about an ice age. Also trying to understand the cause of ice ages was Swedish scientist Svante Arrhenius (1859-1927). In the 1890s, he reasoned that a small increase in carbon dioxide, say from volcanic eruptions, could warm the air a little. But warmer air would hold more water vapor and that would heat the air more. This is an example of a positive feedback. Arrhenius spent many months calculating the effects of changes in CO 2 and water vapor on global temperatures. While his calculations are crude by today’s standards, he estimated that a doubling of CO 2 in the air would lead to a temperature rise of about 5 or 6 degrees Celsius. LeeGlobalWarming:2 In 1938, Guy Stewart Callendar (1898-1964), a British engineer and amateur climatologist, proposed that global temperature was rising and that the reason is increasing levels of carbon dioxide. He also proposed that industrial emissions from the burning of coal were the reason for the rise. In the 1950s, several scientists worked on Callendar’s idea. They assumed that CO 2 was rising due to human activities and started asking how quickly would it rise and where would it end up. Charles Keeling (1928-2005) developed an instrument to measure carbon dioxide in the air and in 1958 he set it on Mauna Loa in Hawaii where it was far...
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This document was uploaded on 10/27/2011 for the course GEOG 1401 at Texas Tech.
- Fall '08