Chapter 1919.1 Global Change and Earth System Science: An Overview2 goals of Earth sciences:1. Understand how Earth works and how it evolved from a landscape of barren rock to the complex landscape dominated by life we see today2. Apply that understanding to better manage our environment19.2 Tools for Studying Global ChangeThe Geologic RecordSediment deposited in lakes, glaciers, ocean etc. are like the pages of a history bookOrganic material with sediment can be dated This material can also show scientists about past life, climate, etc.Analyze air bubbles in glacial ice to see CO2 concentrations in the atmosphereThis air can be as old as 160,000 yearsReal-Time MonitoringReal-time monitoring: collect data while the process is occurringMethods for monitoring vary with what is being monitoredMathematical ModelsUse of numerical means to represent real-world phenomena and linkages and interactions between processes involvedGlobal Circulation Models (GCMs)Predict changes in atmospheric circulation at a global levelData is arranged into cells (area about the size of Oregon)Provide info necessary to evaluate Earth as a system and point out what we can do to better the future19.3 Earth’s Atmosphere and Climate ChangeClimate- characteristic atmospheric conditions (weather) at a particular region over timeperiods from seasons to decadesGlobal circulation and moving air masses in the atmosphere produce major climactic zonesTroposphere- lower part of atmosphere where weather occursAir temp. and oxygen concentration decrease with altitudeTemperature increases in stratosphere and decreases in mesosphere99% of atmosphere by weight is below altitude of 30kmAtmosphereNitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.03%), others (>0.07%)Most variable part is water vapor (0-4% by volume in lower atmosphere)19.4 Global WarmingGreenhouse EffectTemp of Earth is determined by 3 things:Amount of sun Earth receivesAmount of sunlight Earth reflects and therefore does not absorbAtmospheric retention of reradiated heatEarth gets energy from the Sun by electromagnetic radiationAbsorbed solar energy warms Earth’s atmosphere and surfaceWater vapor, CO2, methane, etc. trap heat This causes the lower atmosphere to be warmer than it would be if the radiation escaped into spaceThis is the Greenhouse effect (GE)Greenhouse Effect is natural, pollution just magnifies itCO2 causes 60% of anthropogenic (human-caused) GECO2 levels: 370ppm and expected to reach 450 ppm by 2050Global Temperature Change(see charts on pg. 617)Why Does Climate Change?Milutin Milankovitch saw variability in Earth’s wobbling ~100,000 year cycleCycles of 40,000 and 20,000 years are result of wobbles in Earth’s axisOcean conveyor belt: northbound 12-13°C waters in Atlantic cool to 2-4°C when they getto Greenland. Water then gets saltier (denser) as it cools and it sinks. The current goes south around Africa and joins ocean currents. This, along with warm air currents over the Atlantic cause the temperature in Europe to be 5-10°C warmer than it otherwise would be.Solar ForcingSolar variation accounts for some variability in Earth’s temperatureRelatively small effect (0.25%)- difference between Medieval Warm Period and Little Ice Age was only a fraction of 1%Volcanic ForcingVolcanic eruptions send particles into the air that produce a net coolingAerosols in the air reduced mean temperatures by 1°CVolcanic forcing is believed to have contributed to Little Ice AgeAnthropogenic ForcingPresent warming greatly exceeds natural variabilitySome cooling due to humans as wellGlobal dimming- particles in the air reduce solar energy by as much as 10%19.5 Potential Effects of Global Climate ChangeSummary:Human activity is increasing greenhouse gasesMean temperature of Earth increased by 0.8°C in past 100 yearsSignificant portion of the increased temperature is due to human activityClimate PatternsRise in temperature can affect rain patterns- Northern areas may become wetter, southern land may become more aridThis is not to say that good growing lands will move North, because growing conditions depend on soil typeRise in temperature may change the frequency and intensity of violent storms. Warming oceans will give more energy to hurricanes. Sea Level RiseEstimated to raise 40-200cm in the next centuryA 40cm increase can cause erosion on beaches of up to 80mChanges in BiosphereMosquitoes that carry deadly diseases are able to migrate farther NorthBird and butterfly migrations are moving northwardSea ice is melting, causing problems for seabirds, polar bears and sealsWarming of shallow waters is causing bleaching of coral reefsStrategies for Reducing the Impact of Global WarmingReduction of carbon emissions will help slow warmingSequestration: harvesting CO2 from power plants and injecting it into the subsurface geological environmentSedimentary rocks that contain salty water (saline aquifers) can sequester large amounts of carbon. These rocks can hold many years of human-produced carbon.Depleted oil and gas fields can be utilized if CO2 is compressed to a mixture of liquid and gas and injected underground. This can enhance recovery of remaining oil and gas into the reservoir. Ongoing sequestration projects in Saskatchewan, Canada and under the North SeaGlobal warming is not an immediate emergency- we have a decade or so to find a solution19.6 Coupling of Global Change Processes: Ozone Depletion and Global WarmingAntarctic polar vortex (counterclockwise rotation of atmosphere)Chlorine and ozone chemical reaction and polar stratospheric clouds where this reaction occursChlorofluorocarbons wander to the stratosphere where UV light breaks off the Cl and reacts with ozone to produce ClO and O2. ClO + O -> Cl +