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Global Warming vs. Ozone Depletion

Global Warming vs. Ozone Depletion. Recap: What causes global warming?. The Greenhouse Effect!. TROPOSPHERE. Remember… greenhouse gases absorb and reemit infrared radiation (thermal radiation). TROPOSPHERE. Greenhouse Gasses (In the TROPOSPHERE).

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Global Warming vs. Ozone Depletion

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  1. Global Warming vs. Ozone Depletion

  2. Recap: What causes global warming?

  3. The Greenhouse Effect! TROPOSPHERE

  4. Remember… greenhouse gases absorb and reemit infrared radiation (thermal radiation) TROPOSPHERE

  5. Greenhouse Gasses (In the TROPOSPHERE) -Carbon Dioxide (CO2)-ex. From combustion of fossil fuels, respiration -Water (H2O) ex. From evaporation -Methane Gas (CH4)- ex. Released from cow burps/farts -Nitrous Oxide (N2O)- ex. Result from denitrifying bacteria in fields with fertilizers -Chlorofluorocarbons (CFCs) –ex. From refrigerants, aerosols -Ozone (O3) –ex. A large component of smog. Formed from sunlight and volatile organic compounds (VOCs) reacting together.

  6. Sunlight plus Cars Equals Photochemical Smog • Photochemical smog is a mixture of air pollutants formed by the reaction of nitrogen oxides and volatile organic hydrocarbons under the influence of sunlight.

  7. Sunlight plus Cars Equals Photochemical Smog • Mexico City is one of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog. Figure 19-4

  8. Electromagnetic Radiation

  9. Earth’s Atmosphere

  10. OZONE DEPLETION IN THE STRATOSPHERE -The ozone layer in the upper stratosphere protects us from harmful UV radiaton. -It is getting degraded at a rate of approximately 4% per decade. Figure 20-19

  11. OZONE DEPLETION IN THE STRATOSPHERE • Less ozone in the stratosphere allows for more harmful UV radiation to reach the earth’s surface. • The ozone layer keeps about 95% of the sun’s harmful UV radiation from reaching the earth’s surface. • Chlorofluorocarbon (CFCs) have lowered the average concentrations of ozone in the stratosphere.

  12. Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breaking off a chlorine atom and leaving CFCl2. Sun Cl Once free, the chlorine atom is off to attack another ozone molecule and begin the cycle again. UV radiation A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2. The chlorine atom attacks an ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2). The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). Summary of Reactions CCl3F + UV Cl + CCl2F Cl + O3 ClO + O2 Cl + O Cl + O2 Repeated many times Fig. 20-18, p. 486

  13. Why are ozone “holes” concentrated at the poles? The chemical reactions that lead to ozone depletion only occur in very cold temperatures (-78 OC) in Polar Stratospheric Clouds. Therefore, the “holes” are the largest at the end of the winter, when temperatures have been the coldest.

  14. OZONE DEPLETION IN THE STRATOSPHERE • Since 1976, in Antarctica, ozone levels have markedly decreased during October. Figure 20-20

  15. This long-wavelength (low-energy) form of UV radiation causes aging of the skin, tanning, and sometimes sunburn. It penetrates deeply and may contribute to skin cancer. This shorter-wavelength (high-energy) form of UV radiation causes sunburn, premature aging, and wrinkling. It is largely responsible for basal and squamous cell carcinomas and plays a role in malignant melanoma. Ultraviolet A Ultraviolet B Thin layer of dead cells Hair Squamous cells Epidermis Basal layer Sweat gland Melanocyte cells Dermis Basalcell Blood vessels Squamous Cell Carcinoma Melanoma Basal Cell Carcinoma Fig. 20-22, p. 489

  16. Effects of Ozone Depletion -Sunburns -Skin Cancer -Cataracts -Immune System Suppression -Decreased crop yields -Reduced seafood due to lack of phytoplankton -Less photosynthesis from phytoplankton

  17. Global Warming and Ozone Depletion Indirect relationship: Ozone depletion increases the amount of UV radiation that hits the surface of the earth. Phytoplankton (Algae) are very susceptible to radiation and die. As a result, there is less photosynthesis, and more CO2 accumulates.

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