Lecture 8Outline of Last Lecture I. Cloud FormationII. Mountains and PrecipitationIII. Cloud DropletsIV. Collision and Coalescence V. Cloud DepthVI. Supercooled waterVII. Vapor PressureVIII. The Bergeron ProcessIX. Cold-Cloud ProcessX. Rain and DrizzleXI. VirgaXII. SnowXIII. SleetXIV. Freezing RainOutline of Current Lecture XV. ClimateXVI. Climate Changes with TimeXVII. Climate of Past 130 Years (Instrumental Record)XVIII. Global Warming-- Possible CausesXIX. Continental DriftXX.Milankovitch CyclesATMS 100 1st EditionXXI. Solar VariabilityXXII. VolcanismXXIII. Past Climate: Natural Climate Forcing Agents OnlyXXIV. Anthropogenic AerosolsXXV. Greenhouse Gases: Selective IR AbsorbersXXVI. Past Climate: Natural and Anthropogenic Forcing AgentsXXVII. Global Warming RecapXXVIII. CO2 Emissions ScenariosXXIX. Why Uncertainty?XXX. Where will warming happen?XXXI. Melting Glaciers on LandXXXII. Sea Level RiseXXXIII. Perceiving Climate ChangeXXXIV. Climate Change and Extreme WeatherXXXV. What You Can Do: Energy ConservationCurrent LectureXXXVI. Climatea. long term average of weatherb. varies from place to placeXXXVII. Climate Changes with Timea. ice and snow is reflectiveThese 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.i. high albedoii. additional cooling affectXXXVIII. Climate of Past 130 Years (Instrumental Record)a. Constant from 40’s-70’sb. Rapid period of warming about 1980 (1 degree Celsius)i. Where has it happened?1. not the same every where on Eartha. Mostly Arctic AreasXXXIX. Global Warming-- Possible Causesa. Continental driftb. changes in earth’s orbitc. solar variabilityd. volcanoese. aerosols f. increases in greenhouse gases (Carbon Dioxide)XL. Continental Drifta. as the continents move around the earth, their climates shifti. a continent that moves poleward will coolXLI. Milankovitch Cycles: Changes in Earth’s Orbita. eccentricity: round vs elliptical orbiti. cycles every 100,000 yearsb. axial tilt: tilt of axis varies between 21.8 degrees and 24.4 degreesi. more tilt=greater seasonality1. cycles every 41,000 yearsc. precessioni. which hemisphere is closest to the sun when the earth is closest to the sun?ii. cycles every 22,000 yearsiii. together these cycles lead to ice ages over thousands of yearsiv. NOT CAUSE OF GLOBAL WARMINGXLII. Solar Variabilitya. the sun gradually gets brighter throughout its lifetime (billions of years)b. sun spot cyclesi. reaches maximum every 11 yearsii. long term variations (poorly understood)iii. small fluctuations in solar outputiv. contributed to early 20th century warming but not recentXLIII. Volcanisma. cooling effect: aerosols enter stratosphere and reflect more sunlightXLIV. Past Climate: Natural Climate Forcing Agents Onlya. climate models are unable to replicate recent warming with natural forcing agents aloneXLV. Anthropogenic Aerosolsa. Aerosols: solid or liquid particles suspended in the airb. aerosols can block out the suni. create smogc. possibly responsible for slight global cooling observed between 1940-1980d. sources: pollution, volcanoes, dust, smokeXLVI. Greenhouse Gases: Selective IR Absorbersa. Nitrus oxide, methane, molecular oxygen and ozone, water vapor, carbon dioxideXLVII. Past Climate: Natural and Anthropogenic Forcing Agentsa. we need to account for increasing CO2 to simulate observed warming over past 100 yearsXLVIII. Global Warming Recapa. earth has warmed about 2 degrees over last 100 yearsb. increased greenhouse gas concentrations due to burning fossil fuels are very likely the cause of most of this warmingc. warming is not uniform in space or timei. there are natural climate variabilities responsible for year to year temperature changes1. last winter was colder than mostXLIX. Carbon Dioxide Emissions Scenariosa. How much will we emit each year in the future?i. depends on:1. population2. economy3. energy sources4. human behaviorii. these factors generally not related to atmospheric sciencesiii. source of uncertainty in climate forecastsL. Why Uncertainty?a. natural part of science!!b. all else being equal-- more CO2 will yield a warmer climateLI. Where Will Warming Happen?a. The ArcticLII. Melting Glaciers on Landa. melting glaciers on land contribute to sea level riseb. melting sea ice does NOTLIII. Sea Level Risea. melting ice on land increases sea levelsb. water also expands as it is heatedc. projected sea level rise of .6 to 1.6 feet by 2100 using middle of the road emissions scenariod. maximum rise could be 3 feet by 2100LIV. Perceiving Climate Changea. anthropogenic climate change is real, but cannot be seen by looking out the windowLV. Climate Change and Extreme Weathera. under global warming, it is likely that:i. very hot days more likelyii. very cold days less likelyiii. regional patterns of precipitation will shiftiv. droughts and flooding events become 3-10% more intensev. tropical cyclones become more intensevi. blizzards less likelyb. it is unknown what effect global will have on:i. number of tropical cyclonesii. mid-latitude low pressure systemsiii. thunderstorms, hailstorms, tornadoes, etc.LVI. What You can Do: Energy Conservationa. use less coal, oil, gas (emits less CO2)b. use more renewable energyc. climate scientists: please cut out