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Ozone depletion lect-7.pptx

  1. 1. Ozone depletion by Dr. Jeevan Jyoti, PhD Asst. Professor,
  2. 2. OZONE LAYER DEPLETION • Why hole in the atmospheric ozone layer above us? • What has been done about this? • Why should we worry ourselves about the Ozone Layer Depletion? Mr. OZONE Will I be able to continue enjoying this life without problems?
  3. 3. History of the Ozone Discovery • Dramatic loss of ozone (in stratosphere) over Antarctica was first noticed in the 1970s by a research group from the British Antarctic Survey (BAS) who were monitoring the atmosphere above Antarctica. • When the measurements were taken in 1985, the drop in ozone levels in the stratosphere was so dramatic that at first the scientists thought their instruments were faulty. • Replacement instruments were built and flown out, and it confirmed the earlier measurements, several months later, that the ozone depletion observed was accepted as genuine.
  4. 4. What is ozone? • Ozone (O3 : 3 oxygen atoms) occurs naturally in the atmosphere. • Ozone forms a layer in the stratosphere, thinnest in the tropics (around the equator) and denser towards the poles • measured in Dobson units (DU)
  5. 5. What is a Dobson unit? • 1 Dobson Unit (DU) is defined to be 0.01 mm thickness at STP - (0C and 1 atm press). • The unit is named after G.M.B. Dobson, one of the first scientists to investigate atmospheric ozone. • He designed the 'Dobson Spectrometer'
  6. 6. How is ozone formed? UV radiation strikes the O2 molecule and splits it, atomic oxygen associates itself with another O2 molecule. Ozone (O3) is a highly-reactive form of oxygen.
  7. 7. • Unlike oxygen (O2), ozone has a strong scent and is blue in color. • Ozone exists within both the tropospheric and stratospheric zones of the Earth’s atmosphere • In the troposphere, ground level ozone is a major air pollutant and primary constituent of photochemical smog. • In the stratosphere, the ozone layer is an essential protector of life on earth as it absorbs harmful UV radiation before it reaches the earth.
  8. 8. Where is ozone the “good guy”? trophosphere stratosphere
  9. 9. Where is ozone the “bad guy”? trophosphere stratosphere
  10. 10. CFC’s and ozone depletion • Chlorofluorocarbons are used in refrigerators and air conditioners. • These chlorofluorocarbons are not harmful to humans and have been a benefit to us. • Once released into the atmosphere, CFC are bombarded and destroyed by ultraviolet rays. • In the process chlorine is released to destroy the ozone molecules.
  11. 11. Destruction of ozone by chlorine • Molecular oxygen is broken down in the stratosphere by solar radiation to yield atomic oxygen, which then combines with molecular oxygen to produce ozone. • The ozone is then destroyed by chlorine atoms.
  12. 12. The ozone depletion process
  13. 13. Responsibility for ozone damage each year
  14. 14. Effects of UV rays on Aquatic Ecosystems Ozone depletion causes increases in UV ray’s effects on aquatic ecosystems by: 1. decreasing the abundance of phytoplankton – affects the food stock for fishes and the absorption of CO2 2. decreasing the diversity of aquatic organisms – reduces food stock and also destroys several fish and amphibians.
  15. 15. Effects of UV rays on Terrestrial Ecosystems • Damage to plant cell DNA molecules - makes plants more susceptible to pathogens and pests • Reductions in photosynthetic capacity in the plant - results in slower growth and smaller leaves • Causes mutations in mammalian cells and destroys membranes
  16. 16. Harmful effects of UV rays on people • Skin cancer • Premature aging (photoaging) of the skin. • Cataracts and eye disorders (corneal sunburn and blindness)
  17. 17. Global warming Will Human-Induced Climate Change Destroy the World?
  18. 18. Introduction • Is the world getting warmer? • If so, are the actions of mankind to blame for earth’s temperature increases? • What can/should be done about these issues?
  19. 19. Sun Earth’s Temperature Solar Energy Solar Energy
  20. 20. Sun Earth’s Temperature Solar Energy Radiative Cooling
  21. 21. Sun Earth’s Temperature Solar Energy Radiative Cooling
  22. 22. Sun Earth’s Temperature Solar Energy Radiative Cooling
  23. 23. “Hockey Stick” Controversy 1000 1200 1400 1600 1800 2000 -0.8 Year -0.6 -0.4 -0.2 0 0.2 0.4 0.6 Temperature Change (°C) Direct temperature measurements Michael Mann et al. 1999 The graph is basically flat, other than the rapid increase of temp. during the 20th century. The study received wide acclaim, especially after publication by the IPCC (Intergovernmental Panel on Climate Change) and is now referred to as the “Hockey Stick Graph”.
  24. 24. Ice Sheets Melting? • GRACE (an NGO) found melting of Antarctica equivalent to sea level rise of 0.4 mm/year (2 in/century) • 2005 (by satellite radar pictures) –confirmed Antarctica melting
  25. 25. How Much Temperature Increase? • Some models propose up to 9°C increase this century • Two studies put the minimum at 1.5°C and maximum at 4.5°C or 6.2°C • Another study puts the minimum at 2.5°C
  26. 26. Melting Glaciers – Mt. Kilimanjaro
  27. 27. Ganga under threat fromwarming • Himalayan source of the Ganga is drying up at a rate of 40 yards a year, nearly twice as fast as two decades ago, and that some of these glaciers might disappear by 2030. • In the dry summer months, the Gangotri glacier provides up to 70 % of the water of the Ganga. • According to a UN climate report, the shrinking glaciers also threaten Asia’s supply of fresh water.
  28. 28. Source: New Indian Express
  29. 29. Other ecological effects • The Common Murre has advanced breeding by 24 days per decade over the past 50 years in response to higher temperatures.
  30. 30. • The Baltimore oriole is shifting northward and may soon disappear entirely from the Baltimore area.
  31. 31. • Polar bear populations are coming under threat as food becomes harder to hunt. –Require pack ice to live –Might eventually go extinct.
  32. 32. Sea turtles –Breed on the same islands as their birth –Could go extinct on some islands as beaches are flooded
  33. 33. Drought in Africa Lake Faguibine Lake Chad
  34. 34. Portage Glacier 1914 2004 • Alaska Photos: NOAA Photo Collection and Gary Braasch –
  35. 35. Colorado River • Arizona June 2002 Dec 2003
  36. 36. We can stop global warming!
  37. 37. Mitigation of Global Warming • Conservation – Reduce energy needs – Recycling – Reuse • Alternate energy sources – Nuclear – Wind – Geothermal – Hydroelectric – Solar – Fusion?