GEOL 101 1nd Edition Lecture 26 Outline of Last Lecture I Weather v Climate II Earth as a System III Data IV Oxygen Isotopes Outline of Current Lecture I Atmospheric Heating II Natural Climate Change III Anthropogenic Climate Change Current Lecture Atmospheric Heating Climate is dependent on conditions within the atmosphere Changes within the atmosphere will directly impact climate Energy from the sun Orbital cycles Axial tilt Sunspots Albedo Atmospheric composition Greenhouse gases Primary concerns are CO2 and methane Though small by percentage GHGs have the ability to absorb heat energy Solar radiation is either absorbed by the Earth and atmosphere or it is reflected back into space What can change this from an earth systems perspective More less cloud cover These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute More less ice cover More less vegetation More less volcanic output More less green house gases Higher lower sea level More less aerosols tiny solid or liquid particles suspended in the atmosphere The percentage of energy reflected back into space is called albedo Dark materials absorb more heat energy o Dark rocks vegetation dark colored buildings Lighter materials reflect more heat energy o Light colored rocks snow clouds light colored buildings Albedo can result in positive and negative feedback loops Positive feedback Components amplify each other resulting in run away train effect Negative feedback Components mute each other resulting in equilibrium Positive feedback loop Snowball Earth During the Proterozoic 650 850 Ma there were three major glaciations nearly or completely covered the planet with ice and snow o Much of the continental landmasses were clustered around the south pole which enabled widespread glaciation o widespread glaciation resulted in high albedo and high reflecting of solar radiation o high reflectivity resulted in overall global cooling which resulted in more glaciation o Repeat Repeat Repeat We broke out of the cycle by the build up of CO2 and methane green house gases from volcanoes and a positive feedback loop the other direction Negative feedback loop clouds and air temperature Increased global warming results in more evaporation more evaporation leads to increased cloud cover increased cloud cover results in higher albedo and higher reflectivity of solar radiation high reflectivity results in atmospheric cooling cooler atmospheric conditions result in less evaporation less evaporation results in less cloud cover etc Greenhouse Gases gases in the atmosphere that absorb and radiate heat evergy from the sun These include water vapor and clouds CO2 methane N2O and ozone These make up a very small percentage of Earth s atmosphere but are extremely important Incoming solar radiation gets absorbed by the surface and reemitted as infrared radiation e g heat energy GHGs in the atmosphere absorb that radiation keeping that heat energy in the lower atmosphere Without Greenhouse gases the Earth would be too cold to support life Major concerns about GHGs come from anthropogenic GHG emissions Natural Climate Change We know that the earth s climate has changed dramatically throughout geologic time Natural causes of climate change Tectonic Plates Positions equator vs poles o Changes oceanic circulation heat transfer o Changes albedo potential for glaciation Orbital Cycles o Eccentricity obliquity precession Milankovitch cycles Volcanic Activity ash dust volcanic gases Solar activity and Sunspots widely debated hypotheses that sunspot cycles are linked to temperature and precipitation variations o Possible but no concrete evidence to support either Orbital Cycles Orbital Cycles eccentricity obliquity and precession affect the distribution of solar energy in Earths surface Milutin Milankovitch theorized that variations in orbital geometry could dramatically affect earth s climate He developed a mathematical model and calculated the variations back through time The cycles correspond to major stages as seen from ice core and foraminifera oxygen isotope data over the past million years These cycles are referred to as Milankovich Cycles The mathematical model is not a perfect predictor due to the influence of other factors associated with climate change Volcanoes Volcanic eruptions release ash and dust into the atmosphere This can reflect solar radiation back into space causing short term global cooling until ash and dust settle CO2 released can also result in cloud seeding when CO2 combines with water vapor in the atmosphere higher reflectivity cooler temperature Following several major eruptions there have been measureable decreases in global temperature by to 1 degree F for 2 3 years Volcanic activity also releases CO2 a GHG into the atmosphere Periods of abnormally high volcanic activity may result in global warming as more CO2 is emitted Deccan Traps India huge flood basalts Large Igneous Province LIPs Began erupting towards the end of the Cretaceous period 68 Ma 6 500 ft thick Nearly 200 000 mi2 Unusually high CO2 levels would have accompanied these eruptions May have contributed to the K Pg mass extinction The Siberian Traps in Russia are another flood basalt LIP 8 times the size of Texas Flood basalts began erupting during the late Permian 252 Ma In some areas magma intruded into layer of limestone dolostone halite and other evaporate rocks Contact metamorphism of these layers released GHGs methane butane benzene sulfurbearing gases halocarbons and chlorofluorocarbons into the atmosphere This likely triggered one of the most dramatic climate shifts in geologic history from an ice house to a super hot house One of the likely causes for the Permian Triassic mass extinction 90 of life gone Anthropogenic Climate Change Anthropogenic relating to or resulting from the influence of human beings on nature Humans have been altering the climate as far back as 12 000 years ago with the Neolithic agricultural revolution o Clearing forests for crops and permanent settlements o Domesticating grazing animals o burning wood human generated aerosols and CO2 emissions The Industrial Revolution o Began in mid 1700s o Widespread industrialization in Europe and N America o Switch from burning wood to coal Byproducts of burning coal CO2 largest contribution of anthroporgenic CO2 in atmosphere comes from burning coal Other GHGs N2O SO2 methane particulates and aerosols Post