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Greenhouse effect 1


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Greenhouse effect 1

  1. 1. Greenhouse Effect
  2. 2. Greenhouse Effect <ul><li>The greenhouse effect is the process in which the emission of infrared radiation by an atmosphere warms a planet's surface. </li></ul><ul><li>The Earth's average surface temperature is about 25°C warmer than it would be without the greenhouse effect </li></ul>
  3. 3. Greenhouse Effect <ul><li>The Earth receives energy from the Sun in the form of radiation. </li></ul><ul><li>The Earth reflects about 30% of the incident solar flux. </li></ul><ul><li>The remaining 70% is absorbed, warming the land, atmosphere and oceans. </li></ul>
  4. 4. Greenhouse Effect <ul><li>Solar Energy (sunlight) is short-wavelength radiation which easily penetrates the Earth's atmosphere and warms the Earth. </li></ul><ul><li>Only about one quarter of incoming sunlight is reflected by the atmosphere. </li></ul><ul><li>The warmed Earth emits long-wavelength radiation (infrared waves or heat energy) back into space. </li></ul><ul><li>These longer waves are mostly reflected back to Earth by the atmosphere. </li></ul>
  5. 5. Greenhouse Gases
  6. 6. Carbon dioxide <ul><li>In the last 200 years, because of human activities the proportion of CO 2 has risen from 280 ppm to 360 ppm. </li></ul><ul><li>The proportion of CO 2 has risen by 27% since the beginning of the industrial revolution, when we started to burn coal rather than wood to fuel civilization. </li></ul><ul><li>At present, it is increasing by about 3 ppm a year. </li></ul>
  7. 7. Methane <ul><li>Methane has a much greater warming effect, about 21 times that of carbon dioxide by volume. </li></ul><ul><li>Methane has increased 145% over the last 200 years. </li></ul><ul><li>Despite its greater potential for green house effect, scientists seem less bothered about the rise in methane than that of carbon dioxide. </li></ul><ul><li>The reason is that carbon dioxide survives longer in the atmosphere than methane (between 50 and 200 years) </li></ul><ul><li>Methane is destroyed by chemical processes within 12 – 17 years. </li></ul>
  8. 8. Nitrous Oxide <ul><li>Nitrous oxide is over 200 times more powerful greenhouse gas than CO 2 on a per molecule basis. </li></ul><ul><li>Its greenhouse role is minor compared with other greenhouse gases, but has a relatively long atmospheric life of 120 years. </li></ul><ul><li>The volume is steadily growing at about 0.25% a year. </li></ul><ul><li>The gas is produced in the ground following the application of ammonia based fertilizers. </li></ul><ul><li>Various industrial processes also gives off nitrous oxide. </li></ul>
  9. 9. Chlorofluro carbons <ul><li>CFCs were invented by Thomas Midgley in 1930 and has been extensively used in refrigerators and air conditioners all over the world. </li></ul><ul><li>It has also been used to blow foams and aerosol sprays. </li></ul><ul><li>A CFC molecule added to the atmosphere has a greenhouse effect 5000 times greater than that of an added molecule of CO 2 . </li></ul><ul><li>This means that despite their tiny concentration, compared with CO 2 , they have a significant impact. </li></ul><ul><li>They have a long life span of 100 years. </li></ul>
  10. 10. Ozone <ul><li>Ozone acts as a shield in the stratosphere, protecting us from the harmful effects of UV rays. </li></ul><ul><li>But in the troposphere it function as a green house gas. </li></ul><ul><li>Emission of oxides of nitrogen and hydrocarbons from power stations and vehicles is increasing the concentration of Ozone in the lower atmosphere. </li></ul><ul><li>It has been calculated that a doubling in its concentrations throughout the entire troposphere would lead to a one degree increase in surface air temperature. </li></ul>