Environmental Science: Toward a Sustainable Future Richard T. Wright

1. Environmental Science: Toward a Sustainable FutureRichard T. Wright Chapter 20 The Atmosphere: Climate, Climate Change, and Ozone DepletionPPT by Clark E. Adams

2. El Niño: What Happened? • Jet streams shifted from normal course • Cause unknown April May June

3. El Niño: What Happened? • Development of warm water in the eastern Pacific over time • Reversal in trade winds that normally blow from an easterly direction

4. El Niño: What Happened? • Warm water spread to the east • Global patterns in moisture and evaporation changed = climate shifts

5. The El Niño Effects: Fig. 20-1 • Landslides on the California coast • Mildest hurricane season in many years • Rain five times normal in an East Africa drought region • Record crop harvests in India, Australia, and Argentina

6. La Niña: What Happened? • Easterly trade winds reestablished with greater intensity • Upwelling of colder water from ocean depths • Jet streams are weakened • Global patterns in moisture and evaporation return to “normal”

7. The Atmosphere: Climate, Climate Change, and Ozone Depletion • Atmosphere and weather • Climate • Global climate change • Response to climate change • Depletion of the ozone layer

8. Atmosphere and Weather • Atmospheric structure • Weather

9. Atmospheric Structure

11. Weather: Solar Energy Balance Most solar energy absorbed by atmosphere, oceans, and land

12. Weather: Convection Cell

13. Tornadoes • Cold low-pressure air mass collides with a warm high-pressure air mass http://www.photolib.noaa.gov/nssl/nssl0065.htm

14. Fujita Scale Measures the Intensity of Tornadoes • F-0: 40–72 mph, chimney damage, tree branches broken • F-1: 73–112 mph, mobile homes pushed off foundations or overturned • F-2: 113–157 mph, considerable damage, mobile homes demolished, trees uprooted

15. Fujita Scale Measures the Intensity of Tornadoes • F-3: 158–205 mph, roofs and walls torn down, trains overturned, cars thrown • F-4: 207–260 mph, well-constructed walls leveled • F-5: 261–318 mph, homes lifted off foundation and carried considerable distances, autos thrown as far as 100 meters

16. Climate • Ocean and atmosphere • Climates in the past

17. Climate • Defined as the average trend in temperature and rainfall that produces a unique assemblage of plants and animals • On the next slide identify climates A to E, e.g., low average rainfall and high average temperature = hot desert

18. High A D C Temperature B E Low High Identify Climates A to E Precipitation

19. Climates in the Past

20. Past Climates

21. Ocean and Atmosphere • Covers 75% of the Earth’s surface • Major source of water to hydrologic cycle • Major source of heat to atmosphere • Stores and conveys heat

22. The Ocean Conveyor System

23. The Ocean Conveyor System • Thermohaline circulation: effects that temperature and salinity have on density of water • Conveyor system moves water masses from the surface to deep oceans and back again • Cool northern waters more dense and sink to depths of 4,000 m = North Atlantic Deep Water (NADW)

24. The Ocean Conveyor System • Deep water spreads southward to south Africa and joined by cold Antarctic waters • Spread northward into Indian and Pacific oceans as deep currents • Current slows down, warms up, becomes less dense, rises to the surface, and moves back to North Atlantic • Produces a warm climate in Europe

25. The Ocean Conveyor System • Factors that could alter the conveyor system • Appearance of unusually large quantities of freshwater – melting icebergs • Global warming

26. Global Climate Change • The Earth as a greenhouse • The greenhouse gases • Evidence of climate change

27. The Earth as a Greenhouse

28. Factors Affecting Global Temperatures • Cloud cover: cooling • Changes in Sun’s intensity: cooling or warming • Volcanic activity: cooling • Sulfate aerosols: cooling

29. Greenhouse Gases: CO2 Emissions from Fossil Fuel Burning • 35% higher than before industrial revolution • Oceans = CO2 sink • Forests = CO2 source • 24 billion metric tons CO2 added each year

30. Water vapor Methane Nitrous oxide CFCs and other halocarbons Hydrologic cycle Animal husbandry Chemical fertilizers* Refrigerants* Other Greenhouse Gases and Sources * = Long residence times and contribute to ozone depletion

31. Atmospheric CO2 Concentrations

33. Global Surface Temperatures

34. Global Carbon Cycle

35. Impacts of Global Warming • Melting of polar ice caps • Flooding of coastal areas • Massive migrations of people inland

36. Impacts of Global Warming • Alteration of rainfall patterns • Deserts becoming farmland and farmland becoming deserts • Significant losses in crop yields

37. Evidences of Climatic Change • 17 of the hottest years on record have occurred since 1980 (Fig. 20-5) • Wide-scale recession of glaciers • Sea level rising Predicted mean global temperature change by 2100 is between 1.5 and 4.5oC

38. Reducing CO2 Emissions (True or False) • Reducing use of fossil fuels • Adopt a wait-and-see attitude • Develop alternative energy sources • Plant trees • Examine other possible causes of global warming

39. Reducing CO2 Emissions (True or False) • Make and enforce energy conservation rules • Rely on the government • Adopt the precautionary principle • Raise the minimum driving age to 18 years

40. Key Findings of the 2000 U.S. Climate Change Assessment (Table 20-3) • Increased warming • Differing regional impacts • Vulnerable ecosystems • Widespread water concerns • Agriculture largely unaffected • Forest growth to increase • Coastlines – rising sea levels

41. Responses to Climate Change • Response 1: mitigation = reduce CO2 emissions • Response 2: adaptation = accepting and learning to live with the consequences of climate change

42. Framework Convention on Climate Change (FCC) • Relied on voluntary approach to reduce CO2 emissions • Developing countries continue toward developed nation status using fossil fuels

43. Framework Convention on Climate Change (FCC) • To achieve a 7% reduction by 2010 requires a 25% reduction of present use • By 2010 CO2 emissions will have increased by 30%

44. Framework Convention on Climate Change (FCC) • Bottom line: need 60% reduction (144 ppm) in CO2 emission worldwide NOW to stabilize greenhouse gas concentrations at today’s levels

45. Depletion of Ozone Layer • Radiation and importance of the shield • Formation and breakdown of the shield • Coming to grips with ozone depletion

46. Good Ozone! Bad Ozone!

47. Electromagnetic Spectrum

48. Radiation and Importance of the Shield • Skin cancer (700,000 new cases each year) • Premature skin aging • Eye damage • Cataracts • Blindness

49. Reaction #1: UV light + O2 O + O Reaction #2: Free O + O2 O3 Reaction #3: Free O + O3 O2 + O2 O + O2 Reaction #4: UV light + O3 Formation of the Ozone Shield

50. Chlorofluorocarbons (CFCs) • Organic molecules in which both chlorine and fluorine atoms replace some of the hydrogen atoms • Sources: • refrigerators and air conditioners • production of plastic foam • cleaner for electronic parts • pressurizing agent in aerosol cans