greenhouse effect & global warming

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Greenhouse Effect & Global Warming. Some Evidence. The global air temperature at the Earth's surface has increased about 0.5 o C during the past century. Sun. Solar Energy. Earth’s Temperature. Greenhouses are used to grow plants, especially in the winter. - PowerPoint PPT Presentation


  • Greenhouse Effect & Global Warming

  • Some EvidenceThe global air temperature at the Earth's surface has increased about 0.5oC during the past century

  • Earths Temperature

  • The Greenhouse Greenhouses are used to grow plants, especially in the winter. The glass panels of the greenhouse let in light but keep heat from escaping. This causes the greenhouse to heat up, like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter.

  • GreenhouseGlass, the material that greenhouse is made of, 1) transmit short-wavelength visible light, 2) absorbs and redirects the longer wavelengths of energy. These two aspects make the greenhouse warmer than outside air temperature.

  • Greenhouse effect of the atmosphere Light from the sun includes the entire visible region and smaller portions of the adjacent UV and infrared regions. Sunlight penetrates the atmosphere and warms the earths surface. Longer wavelength infrared radiation is radiated from the earths surface. A considerable amount of the outgoing IR radiation is absorbed by gases in the atmosphere and reradiated back to earth.The gases in the atmosphere that act like glass in a greenhouse are called greenhouse gases.

  • Natural Greenhouse effectThe natural greenhouse effect causes the mean temperature of the Earth's surface to be about 33oC warmer than it would be if natural greenhouse gases were not present.

  • Enhanced greenhouse effectWhen concentrations of greenhouse gases increase, more infrared radiation is returned toward the earth and the surface temperature rises.

  • What makes a gas greenhouse gas?Able to absorb infrared lightMust have molecular vibration(s)The molecular vibrations must be non-symmetric, i.e. infrared activeHomonuclear diatomic molecules only have symmetric vibrations. Thats why N2, O2 are not greenhouse gases.

  • What are the major greenhouse gases?H2OCO2CH4N2OO3CFCs

  • Carbon Dioxide

  • Are human beings causing increases in greenhouse gases?

  • CO2 Concentrations at Mauna Loa, HawaiiThe average atmospheric CO2 concentrations observed at Muana Loa, Hawaii increased approximately 40 ppmv between 1958 and 1995.

  • MethaneAtmospheric methane has increased steadily to present day levels; this increase is highly correlated with human population growth and with related activities, including agricultural practices.Rate of increase: 0.9% annually

  • Nitrous oxide (N2O)Rate of increase 0.25%/yearUse of fertilizer increases both nitrification and denitrification increase N2O production

  • CFC-11

  • Is the earth getting warmer?

  • Temperature over the past one centuryThe global air temperature at the Earth's surface has increased about 0.5oC during the past century

  • Temperature over the past 1000 years

  • Carbon Dioxide

  • Sources and sinks of CO2SourcesNatural: respiration of vegetation and soil detritusMan-made: Fossil fuel combustion, deforestationSinks: slow exchange of carbon between surface waters and deep layers of ocean.(Seawater is alkaline while CO2 is acidic The oceans are a vast reservoir of CO2).

  • Worldwide Carbon EmissionsCarbon (109 metric tons)012345678175018001850190019502000Year

  • Future Carbon Dioxide LevelsIncreasing CO2 emissions, especially in China and developing countriesLikely to double within 150 years:Increased coal usageIncreased natural gas usageDecreased petroleum usage (increased cost and decreasing supply)

  • Status of CO2

    Pre-industrial Amount:280 ppmPresent Amount:382 ppm

    Maximum Allowable 450 ppm

    Rate of Change:+2 ppm/year (and growing)

  • Kyoto ProtocolAdopted in 1997Cut CO2 emissions by 5% from 1990 levels for 2008-2012Symbolic only, since cuts will not significantly impact global warming

  • 1702202703203700200000400000600000Time (YBP)CO2 (ppm) Antarctica 25262728293031SST (C) Tropical PacificCO2 Concentration Vs. Temperature

  • More Important Data

  • Greenhouse Effect & Global WarmingThe greenhouse effect & global warming are not the same thing. Global warming refers to a rise in the temperature of the surface of the earth An increase in the concentration of greenhouse gases leads to an increase in the the magnitude of the greenhouse effect. (Called enhanced greenhouse effect) This results in global warming

  • Consequences of global warmingSea level riseBeach erosionCoastal wetland lossLoss of low-lying territoriesWater resources changePrecipitation pattern shiftIncreases instances of heavy precipitation

    Effects on agricultureChanges in the length of growing seasonGrowth of undesirable plant species

  • Consequences of global warming (Continued)Effects on air qualityIncrease in reaction rates and concentrations of certain atmospheric species increase in O3 in urban areas

    Impacts on human healthChanges in patterns of sickness and death.Respiratory problems affected by air quality changeBiodiversitySome species may grow too quick and overshoot their reproductive period (e.g. reef corals)

    Change in the pattern of ocean current

  • Possible Solutions to Global Warming

  • Mitigation of Global WarmingConservationReduce energy needsRecyclingAlternate energy sources


    ***** If amount of solar energy absorbed by the earth is equal to the amount radiated back into space, the earth remains at a constant temperature. *********In the absence of infrared absorbers, the lower atmosphere would be colder and the the higher atmosphere would be warmer.**In the infrared region of the spectrum, the available transitions involve movement of the nuclei in molecular vibration.Because radiation is electromagnetic, its absorption requires that the transition change the electric field within the molecule, that is, the transition must alter the molecules dipole moment.The transition between different modes of molecular vibration must alter the molecules dipole moment.*****Atmospheric methane is a greenhouse gas that has been measured directly since 1983. It has increased steadily to present day levels; this increase is highly correlated with human population growth and with related activities, including agricultural practices.

    *Denitrification: NO3- to N2, N2O is produced as a by product with a N2: N2O ratio 16:1. N2O is also produced in nitrification (NH4+ to NO3-).Natural sources: 4-8Tg N/yr, anthropogenic: 0.1-3 TgN/yr. Most of anthropogenic N2O derives from use of fertilizer, which increases both nitrification and denitrification.***These data were gathered from about 2000 locations around the world. Points on the blue line indicate the differences between the annual temperature averages and the 1951-1980 30-year average. The large jumps between points on this line show that average temperatures vary widely from year to year. Overall, however, average air temperatures at the Earth's surface have increased. The red line was plotted as a 5-year "running average" to smooth out annual jumps and highlight the overall trend. The running average is obtained by averaging the temperatures for a 5-year period.***CO2 released from respiration of vegetation and soil detritus is balance by photosynthesis.*This spike is due to the exponential increase in the use of fossil fuels over the last 150 years. Shown here are emissions of carbon from gas, solid, liquid fuels, and the total carbon emissions. *Future Carbon Emissions will probably increase, especially in China and developing countries This will result in a likely doubling of carbon dioxide levels within 150 years, due to Increased coal usage And increased natural gas usage, although petroleum usage is likely to decrease due to increased cost and decreasing supply **In an effort to reduce carbon emissions, the Kyoto protocol was adopted in 1997. It proposed to cut CO2 emissions by 5% from 1990 levels for period of 2008-2012 However, such minor cuts would be symbolic only, since such cuts would not significantly impact global warming *Is there a correlation between carbon dioxide levels and temperatures? If we compare carbon dioxide measurements from Antarctica with sea surface temperatures from the tropical Pacific, we find that there is a high coincidence of carbon dioxide levels and temperatures in the past. *******Methods of mitigating global warming include Conservation Reduce energy needs, such as electrical usage, petroleum usage, reduced packaging Recycling, which uses less energy to produce products compared to Another way to reduce carbon emissions is to use alternate energy sources, such as Nuclear Wind Geothermal Hydroelectric Solar Fusion?


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