Climate and Climate ChangePowerPoint Presentation‘Anthropogenic’ ChangesOutlineQuestion: What is Climate?Slide 6Slide 7Slide 8Impacts of Climate Change(2) The Earth’s climate systemWhat is the greenhouse Effect?Earth’s Energy BalanceQuestion: Where Does Energy For Climate System Come From?Kicking the System: Radiative ForcingQuestion: What is the most important Greenhouse gas?Slide 16Slide 17Slide 18(4) Understanding Future Climate: Climate ModelingClimate Model ‘Evolution’Slide 21CCSM Past: Last Millennium to 2100CCSM Future: Next 100+ yearsSimulated DT in 2100 (2100-1990)Simulated DPrecip in 2100Slide 27The Gulf Stream & ‘The Day After Tomorrow’Deep Ocean CirculationCCSM Future: Ocean CirculationQuestion: What does the future hold?Summary/ConclusionsWhy Haven’t we done anything?(5) What are the key uncertainties?Uncertainties (1):Low Clouds Over the OceanUncertainties (2):Uncertainties (3):Climate and Climate ChangeAndrew GettelmanNational Center for Atmospheric Research Climate and Global Dynamics DivisionObserved Temperature RecordsIPCC, 3rd Assessment, Summary For Policymakers‘Anthropogenic’ ChangesOutline1. What is Climate?2. Energy Balance & the Greenhouse Effect3. What climates have we observed?4. What do we expect & how we predict climateSummary & Policy ActionQuestion: What is Climate?A. Average Weather (a value)B. Record high and low temperaturesC. The temperature rangeD. Distribution of possible weatherE. Extreme eventsClimate changeand its manifestation in terms of weather(climate extremes)(1) What is Climate?Climate changeand its manifestation in terms of weather(climate extremes)Climate changeand its manifestation in terms of weather(climate extremes)Impacts of Climate ChangeMote et al 2005Observed Change 1950-1997Snowpack Temperature(- +)(- +)(2) The Earth’s climate systemPole EquatorAtmosphereOceanLand/BiosphereWhat is the greenhouse Effect?Greenhouses Trap HeatAnalogous to Atmosphere: • Glass is transparent in Visible• Glass absorbs in InfraredGreenhouse GasesMajor Greenhouse Gases: Water Vapor, Carbon Dioxide, MethaneEarth’s SurfaceStd Energy balance diagram. Earth’s Energy BalanceQuestion: Where Does Energy For Climate System Come From?A. Earth SurfaceB. SunC. Greenhouse GasesD. Deep OceanE. Earth’s interiorKicking the System: Radiative ForcingQuestion: What is the most important Greenhouse gas?A. Carbon Dioxide B. MethaneC. Water VaporD. OzoneE. Sulfur Dioxide(3) What Have we Observed Temperature RecordsIPCC, 3rd Assessment, Summary For PolicymakersIce Cores: PaleoclimateFrom Petit et al, Nature, 1999 data100,000 200,000 300,000 400,000 Years before presentBlack: CO2; Blue: reconstructed temperature; Red: dust. X-axis: time before present (years). Y axis: CO2 ppmv; other curves rescaled to fitAtmospheric CO2400+20-2-4-6-8Temp Change (C)Ice Cores: Paleoclimate (2)Black: CO2; Blue: reconstructed temperature; Red: dust. X-axis: time before present (years). Y axis: CO2 ppmv; other curves rescaled to fitAtmospheric CO2600 600ppmv CO2 by 2060100,000 200,000 300,000 400,000 Years before present400500+20-2-4-6-8Temp Change (C)What We Do1. Try to understand the Earth’s coupled climate system 2. Apply models of the system to scientific & societal questions 3. Provide a basis for prediction of weather and climate(4) Understanding Future Climate:Climate Modeling2000 2005 Climate Model ‘Evolution’Observations: 20th Century Warming Model Solutions with Human ForcingCCSM Past: Last Millennium to 2100Atmospheric CO2 (input) Temperature (output)CCSM Future: Next 100+ yearsAverage of many models: IPCC TAR Fig 20Simulated T in 2100 (2100-1990)Average of many models: IPCC TAR Fig 23>20%>5%Simulated Precip in 2100Impacts of Climate ChangeMote et al 2005Observed Change 1950-1997Snowpack Temperature(- +)(- +)The Gulf Stream & ‘The Day After Tomorrow’Sea Surface TemperatureSea Surface TemperatureDeep Ocean Circulation‘Thermohaline’ circulation : Thermo = Temperature haline= Salt‘The day after tomorrow’Circulation in the N. Atlantic (the Gulfstream)Circulation is ~20 Sv so 2 Sv anomaly is ~10% changeCCSM Future: Ocean Circulation+10%0-10%-20%-30%-40%Question: What does the future hold?A. Sea Level RiseB. More PrecipitationC. Less PrecipitationD. Don’t Know/UncertainE. All of the AboveSummary/Conclusions•‘Small’ Climate Changes = big weather impacts•Greenhouse Gases are important part of system•Past climate records show correlation w/ climate•Current and Forecast Changes are unprecedentedWhy Haven’t we done anything?•Scientific Uncertainties–What don’t we know•Economic Costs & Benefits–How much will it cost to do something?–How much is climate worth in the future?•Political/Economic Systems–Who benefits from current system?-energy balance pictureWater vapor feedback.Cloud feedbacks. Nobody is affected by the mean!(5) What are the key uncertainties?Uncertainties (1):1. Low Clouds over the ocean: Reflect Sunlight (cool) : Dominant EffectTrap heat (warm)Low Clouds Over the Ocean2 Models: Changesare OPPOSITE!Uncertainties (2):2. High Clouds: Dominant effect is that they Trap heat (warm)Uncertainties (3):3. Water Vapor: largest greenhouse gasIncreasing Temp=Increasing water Vapor (more greenhouse)Effect is expected to ‘amplify’ warming through a
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