chapter18

5 times larger than natural release o n2o causes for

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Unformatted text preview: anthropogenic release is currently estimated to be 2.5 times larger than natural release. o N2O: Causes for change: Human: agriculture (chemical fertilizer) Human: car and truck engines O3: protects from UV radiation in stratosphere but is a greenhouse gas and a pollutant in the troposphere Causes for change: Natural: changes in solar activity (in stratosphere) Human: cars and industry (troposphere) CFCs: exclusively of human origin, does not occur naturally; greenhouse gas and destroyer of protecting stratospheric ozone layer; long lived; a single CFC molecule is therefore capable of destroying large amounts of ozone molecules Sources: air conditioning and refrigerators foam insulations until recently: propellant in aerosol spray cans most countries have banned CFCs and other ozone killers but some developing countries still produce CFCs The increase in greenhouse gases since the Industrial Revolution (mid 1700s) caused an increase of radiative forcing by greenhouse gases by 2.43 W/m2. Compare this to a possible increase of 0.3 W/m2 due to changes in solar output. o o 18.1 The Industrial Age and CO2 o o o o o o 
 CO2 measured from trapped bubbles in ice cores for times prior to 1958 and direct measurements in atmosphere since then industrial revolution at the end of 1700s started a steady increase in CO2 increase from 280ppm in 1800 to 370ppm in 2000 to 387ppm in 2008; the increase has accelerated within last 50 years current CO2 level is the highest in last 650,000 years the U.S. have been the major contributor (25% of world's CO2 production!) China and India catching up rapidly, with China surpassing U.S. in 2009 9
 18.2 The Global Increase in Temperature The link between atmospheric CO2 increase and temperature increase is difficult to assess since global temperature depends on many factors, not just the atmospheric content of greenhouse gases. o global temperature rose 1.0°C within last 140 yrs Possible Reasons: millennial warming (<0.02°C) solar warming (0.2°C) industrial revolution (>0.8°C) volcanism (insignificant) o greatest increases in 1910-1945 and since 1976 o Abbott speculates that the first increase is due to increased sun activity (but sunspot maximum was actually in 1950s to 1960s) and lack of volcanism o temperatures decreased between 1940 and 1970; the minimum in 60ies70ies coincides with drop in solar activity o second increase is most likely due to injection of greenhouse gas...
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This document was uploaded on 11/21/2013.

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