GEOL 101 1nd Edition Lecture 26 Outline of Last Lecture I. Weather v. ClimateII. Earth as a SystemIII. DataIV. Oxygen IsotopesOutline of Current Lecture I. Atmospheric HeatingII. Natural Climate ChangeIII. Anthropogenic Climate Change Current LectureAtmospheric 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 coverThese 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 energyo Dark rocks, vegetation, dark colored buildings- Lighter materials reflect more heat energyo 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 snowo 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) fromvolcanoes, 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. poleso Changes oceanic circulation & heat transfero Changes albedo & potential for glaciation- Orbital Cycleso Eccentricity, obliquity, precession  Milankovitch cycles- Volcanic Activity– ash, dust, volcanic gases- Solar activity and Sunspots– widely debated hypotheses that sunspot cycles are linked totemperature 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, sulfur-bearing 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 revolutiono Clearing forests for crops and permanent settlementso Domesticating grazing animalso burning wood  human-generated aerosols and CO2