L07 - 7.1 Chapter 7 Global Warming and Ozone Depletion...

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Chapter 7: Global Warming and Ozone Depletion – Greenhouse effect • Planet Earth is an open system exchanging energy with the outer space (mostly as infrared radiation), keeping a constant average temperature. The balance can be broken either due to an increased gain or loss of energy • The trapping of radiative energy by some gases in the atmosphere possibly leading its warm up is called reenhouse effect 7.1 Ex : Gases such as carbon dioxide , methane , chlorofluorcarbons (CFC) , nitrous oxide and water vapors my accumulate in the atmosphere and prevent the heat to radiate away from Earth leading to an increase of the average temperature to its warm up is called greenhouse effect • The gases responsible for this effect are called greenhouse gases • Atmospheric models predict that doubling the current concentration of greenhouse gases would lead to a 5 ° C increase in the average temperature which would have devastating effect upon the life on Earth
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Physics of Greenhouse Effect – Role of carbon dioxide What determines the warming of a greenhouse? The windows of a greenhouse allow the sunlight to pass, but then the heat (infrared radiation) is trapped inside, since the windows are opaque to the infrared radiation and the walls won’t allow the air to be cooled by air convection How is this applicable to the global warming? This warming mechanism is similar with the warming of Earth due to the accumulation of carbon dioxide in the atmosphere 7.2 Molecules exchange energy in the form of photons. The frequency of the photons that a certain molecule will be able to absorb or emit depends on its physical properties – its is so called resonant frequency O O C Since the resonant frequency of carbon dioxide is in the infrared range, this gas can absorb the heat emitted by Earth (which otherwise would escape to outer space) and re-send it back to the surface (or other molecules), and thus the heat gets trapped in the atmosphere The greenhouse effect associated with CO 2 is a natural phenomenon contributing to the healthy balance of energy of the planet: the problem appears when CO 2 is released in large amount
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Physics of Greenhouse Effect – Carbon dioxide emissions The increase in CO 2 concentration through human activities started with the industrial revolution due to fossil fuel burning 7.2 Ex : For instance, between 1960-2009 the concentration of CO 2 in the atmosphere increased by more than 70 arts per million parts per million However, the amplitude of the role of this dramatic change of concentration in the
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This note was uploaded on 03/19/2012 for the course PHYSICS phy 121 taught by Professor Mario during the Fall '11 term at Miami University.

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L07 - 7.1 Chapter 7 Global Warming and Ozone Depletion...

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