GS106 Overview of Greenhouse Effect I Introduction A Infrared Active Gases Greenhouse Gases 1 Water Vapor 2 Carbon Dioxide 3 Ozone B Greenhouse Process 1 Absorb Thermal Infrared Radiation heat reflected by Earth s surface and atmosphere C II 2 Atmospheric warming warming of Earth surface warming of lower troposphere 3 Net Result average Earth surface temperature 30o C higher than it would be without the Greenhouse process Historic Consideration 1 rapid increase in concentration of Greenhouse gases since the industrial period 1800 s Greenhouse Gases and Earth Atmosphere Energy Balance A Historic Greenhouse Gas Concentrations 1 Carbon Dioxide CO2 a concentrations 1 pre industrial concentration 280 ppm 2 post industrial concentration 1997 364 ppm b 1 Source burning of fossil fuels 1 Carbon Loading 6 5 x 1015 g carbon year 2 loading exceeds uptake of carbon dioxide by atmosphere and oceans a net result carbon dioxide concentrations 2 3 c Carbon Dioxide Sinks removal processes 1 oceanic dissolution 2 burial in soils deep sea sediments calcium carbonate deposits d Residence Times for Anthropogenic Input 1 decades to centuries with 15 30 remaining for thousands of years Methane CH4 a concentrations 1 pre industrial 700 ppb 2 post industrial 1994 1721 ppb b Source 1 fossil fuels a 70 120 x 1012 g CH4 yr 2 Agriculture Landfills a 200 350 x 1012 g CH4 yr c Estimated residence time for anthropogenic input 10 years in atmosphere Nitrogen Oxide N2O a concentrations 1 preindustrial 275 ppb 2 post industrial 1994 312 ppb b B Source agriculture and industry 1 3 8 x 1012 g N yr Greenhouse Processes 1 anthropogenic greenhouse gas increases atmospheric absorption of Infrared Radiation a result 1 warming of troposphere and Earth surface 2 cooling influence on stratosphere b 2 Carbon Dioxide most long lived greenhouse gas in atmosphere most important factor Complex Feedback and Response a global warming induces increased evaporation increases water vapor increases cloud cover increases albedo promotes cooling b local vs global response c feedback systems uncertain complex interaction of variables 2 III Climate Change and Carbon Dioxide Content A Surface Air Temperature 1 historic global temperature monitoring a results increase of 0 3 to 0 6 degree C over past 150 years b temperature increase is variable this is a long term average trend B Climate Temperature Proxy Data 1 tree ring records 2 ice sheets ice caps Glaciers a present on every continent except Australia b geographically distributed regional climate indicators c NOTE glaciers have been notably receeding for the past century globally 3 Ice Records over past several centuries pre industrial greenhouse gas influx a show variations in global warming and cooling w o anthropogenic influence b RESULT many variables influence climate not just greenhouse gases c Carbon Dioxide Records ice bubbles 1 natural variation in atmospheric CO2 80 100 ppm 2 glacial climate correlates to low CO2 3 interglacial climate correlates to high CO2 C IV Disussion 1 paleoclimate data suggests there is natural variation of greenhouse gases outside the influence of anthropogenic activity 2 there is definitely a link between carbon dioxide content and atmospheric heating cooling 3 many variables exist in a complex system 4 historically there is definitely a dramatic increase in CO2 levels in atmosphere Global Response to Climate Change and Greenhouse Effect A Anticipated Effects Results of Modeling Studies 1 increase in mean air temperature a doubling CO2 content increase of 2 deg C 2 increase in levels of evaporation and precipitation a increased heat in atmosphere b increased evaporation c increased rainfall storm intensity d increased flooding 3 melting of ice sheets a e g Greenland Ice Sheet thinning of ice sheet in past decade by up to 1 m yr at lower elevations 3 4 5 rising sea level a tide records for past century 1 mean sea level rise of 18 cm 100 yrs b thermal expansion c volume increase changes in biosphere ecosystems a increase in active growing season at high latitudes V 4 Summary Points A Anthropogenic greenhouse gases have increased significantly during the industrial period B Effects of greenhouse gases expected to exist for up to 1000 s of years C Increased greenhouse gases cause infrared absorption and heating of atmosphere D Global mean air temp have 0 3 0 6 C in past 150 years E Over the past thousands of years climate has changed with little change in CO2 content F Anticipated changes in system due to global warming include 1 increased air temperature 2 increased precipitation and evaporation 3 rising sea level 4 changes in biosphere
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