Greenhouse gases and their effect


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Greenhouse Effect, their contribution, their global warming potential and effect on environment

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Greenhouse gases and their effect

  1. 1. Species Mixing ratio Source Water Vapour 10,000 to 2 ppmv Natural Methane 1.7 ppmv Biogenic Nitrous oxide 310 ppbv Biogenic Carbon monoxide 50-500 ppbv Anthropogenic Ozone 10 ppbv to 10 ppmv Photochemical Halocarbons Few hundred pptv Anthropogenic COMPOSITION OF THE EARTH’S ATMOSPHERE Major Gases Trace Gases Nitrogen 78.08% Oxygen 20.03% Others Argon 0.93%
  2. 2. Gases which make up far less than 1 percent of the atmosphere have a much greater influence on both short-term weather and long- term climate. The less abundant gases (H2O, CO2, CH4, SO2, andN2O) all have an important property. These gases have the ability to absorb thermal energy (heat) emitted by the earth and thus are able to warm the atmosphere. This warming is what is popularly called the "greenhouse effect.“
  3. 3. These gases are called greenhouse gases as without them the surface of the earth would be about 30 degrees Celsius cooler, and far too cold for life, as we know it, to exist. On the other hand, these greenhouse gases are so thermally potent that even proportionately small amounts can cause Earth’s lower atmospheric temperature to rise.
  4. 4. Absorption of energy by greenhouse gases
  5. 5. Energy balance of the earth.
  6. 6. Radiation Balance
  7. 7. Primary Greenhouse Gases: Gas Water vapor (H2O) ~60 Carbon dioxide (CO2) ~26 Ozone (O3) ~8 Methane (CH 4) Nitrous oxide (N2O ) ~6 Other Greenhouse effect contribution (%)
  8. 8. What causes it? Human Impacts- Natural Impacts-
  9. 9. Global Greenhouse Gas Emissions by Gas, 1990–2005 In 2005, estimated worldwide emissions totaled nearly 39 billion metric tons of greenhouse gases, expressed as carbon dioxide equivalents. This represents a 26 percent increase from 1990. . Emissions of carbon dioxide increased by 31 percent, which is particularly important because carbon dioxide accounts for nearly three-fourths of total global emissions. Methane emissions increased the least—10 percent—while emissions of nitrous oxide increased by 14 percent. Emissions of fluorinated gases more than doubled.
  10. 10. Greenhouse Gas SOURCES SINK Importance for climate Carbon Dioxide • Burning of fossil fuel • Land-use change (deforestation) •Ocean Uptake •photosynthesis Absorbs infrared radiation; affects stratospheric O3 Methane •Biomass burning •Enteric fermentation •Rice paddies • Reactions with OH • Microorganisms uptake by soils Absorbs IR; affects tropospheric & stratospheric O3; produces CO2 Nitrous Oxide • Biomass burning • Fossil-fuel combustion • Fertilizers • Removal by soils • Stratospheric photolysis and rxn with O xygen Absorbs IR; affects stratospheric O3 Ozone •Photochemical reactions involving O2 Catalytic chemical reactions involving NOx species. Absorbs UV & IR radiation CFC Industrial production dissociated in stratosphere Absorbs IR; affects stratospheric O3 Sulphur dioxide Volcanoes, Coal and Biomass burning •Dry & wet deposition •Reactions with OH Forms aerosols, which scatter solar radiation
  11. 11. Carbon is extensively recycled through the earth system, including both the terrestrial, biosphere and the oceans. CO2 CARBON CYCLE
  12. 12. Increased volcanism input huge quantities of CO2 into the atmosphere resulting in the increase in temperature (T°) The CO2 Cycle as Earth’s Thermostat T° increase causes increased chemical weathering and marine carbonate deposition which lowers atmospheric CO2
  13. 13. Future Carbon Dioxide Levels  Increasing CO2 emissions, especially in China and developing countries  Likely to double within 150 years: I. Increased coal usage II. Increased natural gas usage III. Decreased petroleum usage (increased cost and decreasing supply) Country Emission Per Capita (Million Metric Tons/yr) (Metric Tons) USA 1577 5.3 China 15100 1.16 Russia 410 2.87 India 383 (coal 70%, oil 21%) 0.35 Japan 336 2.63 Global Average 1.23
  14. 14. CH4  Generally present in low concentration than CO2  Atmospheric lifetime is important , of the long-lived greenhouse gases (LLGHGs), methane has the shortest lifetime (7 to 10 years) , being susceptible to reaction with OH. This figure shows concentrations of methane in the atmosphere from hundreds of thousands of years ago through 2011. The data come from a variety of historical ice core studies and recent air monitoring sites around the world. Each line represents a different data source
  15. 15. N2O  As a major source of NOx in the stratosphere, where it is transported due to long tropospheric lifetime (140 to 190 years)  Sources: nitrification and denirification in soils and aquatic system, fertilizers etc This figure shows concentrations of nitrous oxide in the atmosphere from 100,000 years ago through 2011. The data come from a variety of historical ice core studies and recent air monitoring sites around the world. Each line represents a different data source
  16. 16. O3  Ozone is a triatomic form of oxygen (O2) found in Earth’s upper and lower atmosphere.  The ozone layer, situated in the stratosphere about 15 to 30 km above the earth's surface.  Ozone protects living organisms by absorbing harmful ultraviolet radiation (UVB) from the sun.  03 near the ground is at temperatures close to those of the earth's surface. As a result, emission and absorption are occurring at essentially the same temperature, resulting in no contribution to the greenhouse effect. However, because the temperature falls with altitude up to the tropopause, the Boltzmann distribution shifts to smaller relative populations in the excited states. As a result, the net emission from 03 becomes smaller relative to absorption.
  17. 17. 03 absorbs strongly in the UV as well, which leads to heating in the stratosphere, in contrast to CO2, which cools it. Thus, changes in the concentrations of ozone and its vertical distribution affect not only infrared but also solar UV radiation, with associated effects on climate.
  18. 18. Estimated Global Warming Potential Lifetime 20 years 100 years 500 yearsyears GREENHOUSE GAS Carbon Dioxide (CO2) Variable 1 1 1 Methane (CH4) 12 62 23 7 Nitrous Oxide (N2O) 114 275 296 156 CFCl3 (CFC11) variable 6300 4600 1600 CF2Cl2 (CFC12) variable 10200 10600 5200 Based on Intergovernmental Panel on Climate Change Third Assessment Report, 2001 GWP reflects the relative strength of individual greenhouse gas with respect to its impact on global warming. It was defined as the cumulative radiative forcing between the present and some future time caused by a unit mass of greenhouse gas emitted now, expressed relative to CO2.
  19. 19. Expected Consequences of increased GHG Concentration is: Climate Change GLOBAL WARMING is the increase of the Earth’s average surface temperature due to a build- up of greenhouse gases in the atmosphere. CLIMATE CHANGE is a broader term that refers to long-term changes in climate, including average temperature and precipitation.
  20. 20. • The snow cover in the Northern Hemisphere and floating ice in the Arctic Ocean have decreased • Sea level has risen 4-8 inches over the past century • Global surface temp. could rise 1-4.5°F (0.6-2.5°C) in the next fifty years, and 2.2-10°F (1.4-5.8°C) in the next century Global mean surface temperatures have increased 0.5-1.0°F since the late 19th century
  21. 21. Kyoto Protocol • Framework – stabilize greenhouse gas emissions to prevent anthropogenic interference with the climate system – emission targets for industrialized countries between 2008- 2012 are collectively about 5% lower than 1990 emissions • US target is 7% reduction • developing countries do not have quantified targets – six gases • CO2, CH4, N2O, HFCs, PFCs, SF6 "We must limit global temperature rise to 2 degrees. We are far from there, and even that is enough to cause dire consequences. If we continue along the current path, we are close to a 6 degree increase". - UN Secretary-General Ban Ki-moon Remarks at the Council on Foreign Relations (February 2013)
  22. 22. REFERENCES  2012.pdf  Chemistry of upper and lower atmosphere-Barbara Pitts  Class lecture slides    se_e.pdf