Slide 1Global Warming on the Earth Figures mostly from Professor Bob StromSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Greenhouse Gases for the Past 650,000 YearsAtmospheric CO2 and Population GrowthSlide 12Recent CO2 Increase (1959 - 2007)Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Two Ice SheetsArctic Summer Sea Ice Record Minimum (2007)Slide 29Greenland Melting (1992-2005) (Volume loss (2005) = 240 km3 per year)Greenland Ice Sheet MeltingAntarctic Temperature Changes Between 1981 and 2007Larson B Ice Shelf Collapse (2002)Breakup of the Wilkins Ice Shelf (2008)Slide 35Projected Permafrost Decline by the 2090sSlide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Carbon Emissions for Peak CO2 StabilizationSlide 52Slide 53Slide 54PYTS/ASTR 206 – Global Warming on the Earth1AnnouncementsHW4 due on ThursdayMid-term #2 next weekToday’s lecture a special topic…PYTS/ASTR 206 – Global Warming on the Earth2PTYS/ASTR 206 – The Golden Age of Planetary ExplorationShane Byrne – [email protected] Warming on the EarthFigures mostly from Professor Bob StromPYTS/ASTR 206 – Global Warming on the Earth3In this lecture…In this lecture…What sets the temperature of the Earth?The greenhouse effect revisitedEarth’s carbon dioxideEarth’s temperature recordClimate change todayFeedbacks and tipping pointsConsequences of climate changeOptions at this point?Climate change skeptics and alarmistsPYTS/ASTR 206 – Global Warming on the Earth4Our position in the solar systemSunlight at 1AU~1370 W m-2Solar Luminosity slowly grows with timeEarth’s distance from the Sun is fixedLatitudeMore sunlight when the sun is overheadTropics are hotter than the polesWhat sets the Earth’s temperature?What sets the Earth’s temperature?PYTS/ASTR 206 – Global Warming on the Earth5ReflectionIcy areas stay coolerDark areas warm upClouds are important in keeping Earth coolPYTS/ASTR 206 – Global Warming on the Earth6The greenhouse effect revisitedVisible light hits the planet’s surfaceOutgoing infrared light is blocked by greenhouse gases in the atmosphereTrapped energy keeps the surface and lower atmosphere warmerPYTS/ASTR 206 – Global Warming on the Earth7What are these greenhouse gases?Carbon Dioxide – CO2Methane – CH4Tropospheric Ozone – O3HalocarbonsNitrous Oxide - N2OMethane is much more effective than CO2 but also much less abundantCO2 is the main greenhouse gasVenus has lots of CO2 Big greenhouse effect - very high temperaturesMars has a thin CO2 atmosphereSmall greenhouse effect – a cold planetPYTS/ASTR 206 – Global Warming on the Earth8CO2 on the Earth Earth has water that rainsRain dissolves CO2 from the atmosphereForms carbonic acidThis acidified rainwater weathers away rocksWashes into the ocean and forms carbonate rocks Carbonate rocks eventually recycled by plate tectonicsThe rock-cycle keeps all this in balanceSometimes this gets out of sync e.g. snowball Earth – stops weatheringPYTS/ASTR 206 – Global Warming on the Earth9Causes of Climate Change•Abundance of Greenhouse Gases•Major Volcanic Eruptions•Large Asteroid or Comet Impact•Change in Sun’s Irradiance•Change in Ocean Circulation •Continental Drift•Change in Earth’s MotionsVerySlowVeryUnlikelyPYTS/ASTR 206 – Global Warming on the Earth10Greenhouse Gases for the Past 650,000 YearsPYTS/ASTR 206 – Global Warming on the Earth11Atmospheric CO2 and Population GrowthPYTS/ASTR 206 – Global Warming on the Earth12PYTS/ASTR 206 – Global Warming on the Earth13Recent CO2 Increase (1959 - 2007)PYTS/ASTR 206 – Global Warming on the Earth14Generalized Climates for the Past 3 Billion YearsPYTS/ASTR 206 – Global Warming on the Earth15Hot-houseEquatorial oceans like a hot-tubArctic ocean like the tropics todayNo ice anywhere on EarthPlant life explodesUses up a lot of CO2Ice houseIce sheets covering portions of the EarthReduced plant activityDoesn’t use up much CO2Recent variations in climate caused by Milankovitch cyclesPYTS/ASTR 206 – Global Warming on the Earth16Zooming in furtherTemperatures still going up…end of last ice age?Unfortunately not… the rate of increase is faster than any time in the past (and still increasing)PYTS/ASTR 206 – Global Warming on the Earth17Current global warming coincides withPopulation explosionIndustrial revolutionRapid rise in atmospheric CO2PYTS/ASTR 206 – Global Warming on the Earth18PYTS/ASTR 206 – Global Warming on the Earth19All this fuss for one or two degrees… Really such a big deal ??It’s a big deal because of the possible feedbacks1. Ice2. Permafrost3. Methane Hydrate4. The oceansPYTS/ASTR 206 – Global Warming on the Earth20Feedback #1 – planetary AlbedoIce around the world is retreatingIce reflects most of the energy that falls on it Less ice means warmer temperaturesWarmer temperatures mean even less ice etc etc…PYTS/ASTR 206 – Global Warming on the Earth21Glaciers around the world are shrinkingExamples from AlaskaVegetation changes also indicate climate changeGlaciers are pretty sensitive to climate and so are good indicatorsPYTS/ASTR 206 – Global Warming on the Earth22PYTS/ASTR 206 – Global Warming on the Earth23PYTS/ASTR 206 – Global Warming on the Earth24PYTS/ASTR 206 – Global Warming on the Earth25AndesPYTS/ASTR 206 – Global Warming on the Earth26The decline of the Gangotri Glacier in the Himalaya Mts. of India.PYTS/ASTR 206 – Global Warming on the Earth27Two Ice SheetsPYTS/ASTR 206 – Global Warming on the Earth28Arctic Summer Sea Ice Record Minimum (2007)PYTS/ASTR 206 – Global Warming on the Earth29Volume and area of arctic sea-ice decline precipitously2007 was badPeople predicted an ice-free arctic ocean in 10 yearsPYTS/ASTR 206 – Global Warming on the Earth30Greenland Melting (1992-2005)(Volume loss (2005) = 240 km3 per year)PYTS/ASTR 206 – Global Warming on the Earth31Greenland Ice Sheet MeltingPYTS/ASTR 206 – Global Warming on the Earth32Antarctic Temperature Changes Between 1981 and 2007PYTS/ASTR 206 – Global Warming on the Earth33Larson B Ice Shelf Collapse (2002)PYTS/ASTR 206 – Global Warming on the Earth34Breakup
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