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Air Issues Atmosphere basics Air pollution Climate change Composition of atmosphere 78% nitrogen 21% oxygen 1% everything else Structure of atmosphere Mesosphere and thermosphere 52-120 km Stratosphere 12-52 km temperature increases upward important ozone layer (19-26 km) Troposphere ground to 12 km temperature decreases upward Focus on troposphere Our weather Pollution that affects humans Usual conditions vs. inversions (change in temperature going upward) Usual conditions – pollution rises Inversion – pollution is trapped Air pollution Outdoor air pollution Indoor air pollution Criteria air pollutants (Clean Air Act, EPA) Carbon monoxide NOx or nitrogen dioxide SO2 (sulfur dioxide) tropospheric ozone (O3) particulate matter (PM) lead (Pb) Let’s look at sources of each of these. Carbon monoxide (CO) Incomplete combustion of coal gasoline (catalytic converters help here) Why is it harmful to humans? Nitrogen oxides (many forms) NOx Incomplete burning of gasoline Contributes to acid rain Part of ozone problem in summer in cities Tropospheric Ozone Secondary pollutant Monitor VOCs (volatile organic compounds) solvents and vehicle emissions particularly important Often a summer-time problem Sulfur dioxide (SO2) Burning of coal Volcanic emissions (natural) Effects: damages plant chlorophyll, irritates throat and lungs; causes acid rain Particulate matter Incomplete combustion of fossil fuels Dust from fields, construction, etc. Size of particles important What ARE those particles? Lead Primary source from leaded gasoline Metal processing industries Effects central nervous system and bioaccumulates Criteria Air pollutants Carbon Monoxide Sulfur Dioxide Nitrogen Dioxide Tropospheric Ozone Particulate Matter Lead Primary sources to atmosphere Secondary pollutants Created by a reaction Includes smog and tropospheric ozone Smog Photochemical smog (LA smog) Industrial smog (London smog) Photochemical smog (1) Car exhaust Hydrocarbons and NOx plus solar radiation produces toxic chemicals, particularly ozone Higher ozone concentrations in late summer afternoons Photochemical smog (2) Effects of ozone: Solutions: Ozone (O3) Stratosphere = good; troposphere = bad Part of summertime smog Charlotte area (and many other urban areas) are in non-attainment for ozone levels Industrial smog Older industrial cities Often associated with coal burning Particulates, sulfur dioxide and stagnant air Acid deposition Sulfuric and nitric acids Travel long distances Some solutions: industrial scrubbers, catalytic converters Indoor air quality Increasing awareness Developing countries: particulate matter and carbon monoxide Industrialized nations: cigarette smoke, radon, mold, VOCs Solutions? Global air issues Stratospheric ozone depletion Climate change Stratospheric Ozone Depletion What does stratospheric ozone do? What is happening? 1970s mid 1990s Antarctic Researchers Routinely monitor atmosphere above Antarctica Significant depletion started in 1980 Rowland and Molina Predicted CFCs would destroy ozone (1974) CCl2F2 + UV Cl + CClF2 Cl + O3 ClO + O ClO + O2 O2 + Cl What can we do? Phase out manufacturing of CFCs – done Phase out use of CFCs – spray cans, styrofoam products, refrigerants – done Can this happen on a global basis? Montreal Protocol (1987) Major reduction in production of CFCs and halons Initially signed by 25 nations, eventually ratified by over 150 nations CFC production in industrial nations to be cut by 50% Halon production frozen at 1986 levels SUCCESS Climate Change NATURAL TEMPERATURE VARIABILITY INCLUDING GREEN HOUSE EFFECT HUMAN IMPACT ON TEMPERATURES ADAPTATION, MITIGATION, SUFFERING Natural Temperature Variability Seasons Latitudes - altitudes Milankovitch cycles El Nino cycles How do we know temperatures from long ago? Human records: actual measurements Proxies: ice cores, sediment cores for example Greenhouse effect What is it? Is it bad or good that Earth has a greenhouse effect? Greenhouse gases Sources of greenhouse gases Carbon dioxide : burning fossil fuels and forests, making cement Methane: decomposition of organic matter in swampy environments; frozen in tundra and ocean floor; stomachs of cows Nitrous oxides: bacterial decomposition of manure; soil denitrification; some organic fertilizers Halocarbons (including CFCs): chemical cooling agent; foaming agent; propellant (phased out by Montreal Protocol) Relative strength of GHG (from IPCC, 2007) Carbon Dioxide 1 Methane 25 Nitrous oxide 300 1 CFC replacement 15,000 Future of global warming? Computer modeling United Nations IPCC Intergovernmental Panel on Climate Change •Established in 1988 •2,000 scientists from many nations •Four assessment reports (latest in 2007) •Policy-relevant but policy neutral •Won the Nobel Peace Prize (along with Al Gore) IPCC Fourth Assessment Report Conclusions Greenhouse gases such as carbon dioxide help trap heat near Earth’s surface. IPCC Fourth Assessment Report Conclusions “Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed preindustrial values determined from ice cores spanning many thousands of years.” Today = 385 ppm Preindustrial = 280 ppm Highest in 650,000 years Figure SPM.1 IPCC Fourth Assessment Report Conclusions “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.” Fi Future? Sea level change (3-20 ft rise) Coral reef “bleaching” Changes in locations of plants and animals Melting of ice caps and glaciers Sea Ice in Arctic Ocean 1979 and 2003 Alaskan glacier 1914 and 2004 Solutions? Adaptation Mitigation Suffering is inevitable, but how much? Evaluating Solutions The Need for Adaptation We are already committed to a certain amount of warming Resources must be devoted to adapting to altered future conditions Sea level Ecosystems Focus on mitigation cannot ignore need for adaptation Mitigation? Limit dependence on fossils fuels Plant trees Kyoto Protocol and beyond