Presented To Stanford University Physics And Applied .
Presented toStanford UniversityPhysics and Applied Physics DepartmentColloquiumOctober 5, 2004Burton RichterPaul Pigott Professor in the Physical SciencesStanford UniversityDirector EmeritusStanford Linear Accelerator Center1
Earth from Apollo 17 (NASA)2
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The Greenhouse Effect Solar flux at earth orbit 1.4 kW/m2 Average reflected 30% Average over entire surface ofglobe 240 W/m2 Average temperature of surface 288 K Radiation at 288 K 400 W/m2 Average temperature to radiate240 W/m2 –20 C Water vapor is the maingreenhouse gas Geological heat flux is about 0.1%of solar5
1000 Years of Global CO2 andTemperature ChangeRecords of northern hemisphere surface temperatures, CO2 concentrations, andcarbon emissions show a close correlation. Temperature Change: reconstruction ofannual-average northern hemisphere surface air temperatures derived fromhistorical records, tree rings, and corals (blue), and air temperatures directlymeasured (purple). CO2 Concentrations: record of global CO2 concentration for thelast 1000 years, derived from measurements of CO2 concentration in air bubbles inthe layered ice cores drilled in Antarctica (blue line) and from atmosphericmeasurements since 1957. Carbon Emissions: reconstruction of past emissions of 6CO2 as a result of land clearing and fossil fuel combustion since about 1750 (inbillions of metric tons of carbon per year).
IPCC – Third Assessment Report7
Climate Change 2001:Synthesis ReportFigure SPM-10b: From year 1000 to year 1860 variations in average surface temperature of the NorthernHemisphere are shown (corresponding data from the Southern Hemisphere not available) reconstructed fromproxy data (tree rings, corals, ice cores, and historical records). The line shows the 50-year average, the greyregion the 95% confidence limit in the annual data. From years 1860 to 2000 are shown variations inobservations of globally and annually averaged surface temperature from the instrumental record; the lineshows the decadal average. From years 2000 to 2100 projections of globally averaged surface temperature areshown for the six illustrative SRES scenarios and IS92a using a model with average climate sensitivity. Thegrey region marked “several models all SRES envelope” shows the range of results from the full range of 35SRES scenarios in addition to those from a range of models with different climate sensitivities. The temperaturescale is departure from the 1990 value; the scale is different from that used in Figure SPM-2. Q9 Figure 9-1b8
6A1BSeveral modelsall SRESA1TenvelopeA1FIA2Model ensembleB1all SRESB2envelopeIS92ehigh(TARmethod)IS92aIS92c low54321Bars showtherangein2100producedbyseveral models0200020202040Year2060208021009
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Removal Time and PercentContribution to cOzoneNitrous OxideRoughRemovalTime 100 yearsApproximateContributionin 200660%10 years25%50 days20%100 years5%Fluorocarbons 1000 yearsSulfateAerosolsBlack Carbon 1%10 days-25%10 days 15%13
Projecting EnergyRequirements I E E P P I EPII/PE/I EnergyPopulationIncomePer Capita IncomeEnergy Intensity14
World Population GrowthF ig u r e 7 . W o r ld P o p u la t io n G r o w t h .15
Comparison of GDP(trillions of constant U.S. dollars )andPer Capita in Years 2000 and 2100(thousands of constant U.S. dollars per person)(IIASA Scenario B) (2002 exchange rates)20002100GDP GDP perPersonGDP GDP perPersonIndustrialized 111611.5World26.24.220217.316
Energy Intensity(Watt-year per dollar)(IIASA Scenario B)Watt-year .360.2317
Energy Intensity and CompositeFuel Price in North America18
Three Regions, Scenario B19
SummaryItem200020502100Primary 0Energy Intensity(Watt-years/ )0.520.360.23Assumptions:1. IIASA “Scenario B” (middle growth).2. United Nations’ Population Projection(middle scenario).3. A 1% per year decline in energy intensity isassumed (historic trend).20
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Primary Power Requirements for2050 for Scenarios StabilizingCO2 at 450 ppm and 550 ppm2000Source2050450ppm550ppmCarbonBased11 TW7 TW12 TWCarbon Free3 TW20 TW15 TWM. Hoffert, et al., Nature, 395, p881, (Oct 20, 1998)22
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Final Energy by Sector(IIASA Scenario B)200020502100Residential ion25%27%23%Total (TW-yr)9.819.027.424
Large-Scale Energy SourcesWithout Greenhouse Gases Conservation and Efficiency9 No emissions from what you don’t use. Fossil9 If CO2 can be sequestered, it isuseable.9 Reserves of: Coal are huge Oil are limited Gas are large (but uncertain) in MethaneHydrates. Nuclear9 Climate change problem is revivinginterest.9 400 plants today equivalent to about1-TW primary.9 Major expansion possible IF concernsabout radiation, waste disposal,proliferation, can be relieved. Fusion9 Not for at least fifty years.25
Renewables Geothermal9 Cost effective in limited regions. Hydroelectric9 50% of potential is used now. Solar Photovoltaic and Thermal9 Expensive but applicable in certain areas,even without storage. Photovoltaic is 5 perpeak watt now; expected to be down to 1.5by 2020. Wind9 Cost effective with subsidy (U.S. 1.5 ,Australia 3 , Denmark 3 per kW-hr).Intermittent. Biomass9 Two billion people use non-commercialbiomass now. Things like ethanol from cornare a farm subsidy, not in energy source. Hydrogen9 It is a storage median, not a source.Electrolysis 85% efficient. Membrane fuelcells 65% efficient.26
Power (TW) Required in 2050Versus Rate of Decline in EnergyIntensity27
CO2 Sequestration Most study has been on CO2 injection intounderground reservoirs. Capacity not well knownGigatonCO2Fraction ofIntegratedEmissions to 2050Depleted Gas Fields69034%Depleted Oil Fields1206%400 - 10,00020% - 500%402%OptionDeep Saline AquifersUnmineable Coal28
CO2 Sequestration (Continued) Norway does this on a medium scale. Costs estimates 1– 2 /kW-hr or 100/ton CO2. Leak rates not understood. DOE project FutureGen on Coal H20 H2 CO2 with CO2 sequestrated. Alternative solidification (MgO – MgCO2)in an even earlier state.29
Radiation ExposuresSourceRadiation DoseMillirem/yearNatural Radioactivity240Natural in Body (75kg)*40Medical (average)60Nuclear Plant (1GW electric)0.004Coal Plant (1GW electric)0.003Chernobyl Accident(Austria 1988)24Chernobyl Accident(Austria 1996)7*Included in the NaturalTotal30
Public Health Impacts per TWh*Years of life rPVWind138167359429.1582.7Radiological effects:Normal operationAccidents160.015Respiratory .03Congestive heartfailure0.800.842.10.240.050.330.02Restricted activity days47514976122481446314197790Days withbronchodilatorusage1303136533613978654325Cough days inasthmatics1492156238464549862128Respiratory symptomsin asthmatics69372617862114528813Chronic bronchitis inchildren1151353333911542.4Chronic cough inchildren1481744285114693.2Nonfatal cancer2.4*Kerwitt et al., “Risk Analysis” Vol. 18, No. 4 (1998).31
The Spent Fuel ProblemComponentPer CentOf TotalRadio-activityUntreatedrequiredisolationtime 51IntenseNegligibleMedium2000300,00032
Two-Tier SchematicTwo-Tier SchematicLWRSeparationPlantFast System(one for every 7-10 LWRs)ReprocessedFuelActinidesU&FFRepository33
Impact of Loss FractionImpact of Loss Fraction - Base ATW Case (3M)Relative Toxicity1.00E 041.00E 030.1% Loss1.00E 020.2% Loss0.5% Loss1.00E 011% Loss1.00E 00101001000100001.00E-01Time (years)34
Technical issues controlling repositorycapacity.9 Tunnel wall temperature 200 C.9 Temperature midway between adjacenttunnels 100 C. Fission fragments (particularly Cs and Sr)control in early days, actinides (Pu andAm) in the long term. Examples:9 Removal of all fission fragments does nothingto increase capacity.9 Removal of Cs and Sr (to separate short-termstorage) and Pu and Am (to transmutation)increase capacity sixty fold. Note: Yucca Mountain is estimated tocost about 50 Billion to develop and fill.35
Transmutation Benefits RepositoryTransient Thermal Response36
Decay Heating of Spent Fuel37
Proliferation The “spent fuel standard” is a weak reed.Repositories become potential Pu mines in about100-150 years. For governments, the only barrier to “goingnuclear” is international agreements. Reprocessed material is difficult to turn intoweapons and harder to divert.Isotopic PercentageIsotopeLWRMOXNon-fertile PuPu 238249Pu 23960418Pu 240243438Pu 24191117Pu 242592738
Costs The report, “Nuclear Waste Fund Fee Adequacy:An Assessment, May 2001, DOE/RW-0534”concludes 0.1 per kW-hr remains about right fornuclear waste disposal. CO-2 sequestration is estimated to cost 1-1.5 perkW-hr for gas-fired plants and 2-3 per kW-hr forcoal-fired plants (Freund & Davison, GeneralOverview of Costs, Proceedings of the Workshopon Carbon Dioxide Capture and tml).Modified MIT Study TableItemPower Costs(cents per kWe-hr)NuclearCoalGasCapital & OperationWaste Sequestration4.1 – 6.60.14.22–33.8 – 5.61 – 1.5Total4.2 – 6.76.2 – 7.24.8 – 7.139
Conclusions andRecommendations Energy use will expand. There is no quick fix. A goal needs to be set. Driving down energy intensity should befirst on the list of action items. Emissions trading and reforestationshould be encouraged. Nuclear Power should be expanded. Bringing the renewables to maturityshould be funded. Financial incentives and penalties needto be put in place.40
“Science,” 305, 968 (August 13, 2004)41
Energy and Environment Web Sitesof Interest EPA’s global warming resource center – an annotated list artment of Energy’s Energy InformationAdministration – mostly energy information about the USwith some international. http://www.eia.doe.gov/International Energy Agency’s statistics home page –statistics by region, country fuel, etc. (IEA home page ishttp://www.iea.org/) – they have a particularly interestingnew report on “Biofuels for tats/index.aspWorld Energy Outlook 2004 – an update of long rangeprojections due out at the end of October 2004 (manyuniversity libraries are subscribers to IEA publications andyou may be able to down load this nal Institute of Applied Systems Analysis andWorld Energy Council long range projection – this is from1998 but remains particularly useful in allowing the user tochose different assumptions and see what happens.http://www.iiasa.ac.at/cgi-bin/ecs/book dyn/bookcnt.pyIIASA home http://www.iiasa.ac.at/Intergovernmental Panel on Climate Change – theinternational group responsible for projection on climatechange under different scenarios. Their workshopsaddress specific issues and are the source of muchvaluable information. http://www.ipcc.ch/Nuclear Energy Agency – an arm of the OECD on nuclearissues. http://www.nea.fr/US Climate Change Information Center – the latest reporton the US program. http://www.climatescience.gov/42
Stanford University Physics and Applied Physics Department Colloquium October 5, 2004 Burton Richter Paul Pigott Professor in the Physical Sciences Stanford University Director Emeritus Stanford Linear Accelerator Center. 2 Earth from Apollo 17 (NASA) 3. 4. 5 The Greenhouse Effect Solar
SEISMIC: A Self-Exciting Point Process Model for Predicting Tweet Popularity Qingyuan Zhao Stanford University qyzhao@stanford.edu Murat A. Erdogdu Stanford University erdogdu@stanford.edu Hera Y. He Stanford University yhe1@stanford.edu Anand Rajaraman Stanford University anand@cs.stanford.edu Jure Leskovec Stanford University jure@cs.stanford .
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Stanford University Stanford, CA 94305 bowang@stanford.edu Min Liu Department of Statistics Stanford University Stanford, CA 94305 liumin@stanford.edu Abstract Sentiment analysis is an important task in natural language understanding and has a wide range of real-world applications. The typical sentiment analysis focus on
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