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Why should we be concerned about Global Warming?

Why should we be concerned about Global Warming?. “Why should we be concerned about Global Warming?” . Many people consider that Global Warming is the greatest environmental threat of the 21st Century.

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Why should we be concerned about Global Warming?

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  1. Why should we be concerned about Global Warming?

  2. “Why should we be concerned about Global Warming?” • Many people consider that Global Warming is the greatest environmental threat of the 21st Century. • However, during the 80s and early 90s scientists argued about the causes and effects of global warming. • In the late 1990s scientists reached a consensus that global warming was a cause for concern. • So, why should you be concerned about global warming?

  3. 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? • Are the potential resolutions worth the cost to implement them?

  4. History of Earth’s Climate • Earth formed ~4.6 billion years ago • Originally very hot • Sun’s energy output only 70% of present • Liquid water present ~4.3 billion years ago (zircon dating) • Much of earth’s early history erased during late heavy bombardment (~3.9 billion years ago)

  5. History of Earth’s Climate • Life appeared ~3.8 billion years ago • Photosynthesis began 3.5-2.5 billion years ago • Produced oxygen and removed carbon dioxide and methane (greenhouse gases) • Earth went through periods of cooling (“Snowball Earth”) and warming • Earth began cycles of glacial and interglacial periods ~3 million years ago

  6. Sun Solar Energy Solar Energy Earth’s Temperature

  7. Sun Solar Energy Radiative Cooling Earth’s Temperature

  8. Sun Solar Energy Radiative Cooling Earth’s Temperature

  9. Sun Solar Energy Radiative Cooling Earth’s Temperature

  10. Sun Greenhouse Effect

  11. Nitrogen (N2) Oxygen (O2) Water (H2O) Carbon Dioxide (CO2) Methane (CH4) Earth’s Atmospheric Gases Non-Greenhouse Gases 99% Greenhouse Gases 1%

  12. Sun Venus Runaway Greenhouse Effect • 97% carbon dioxide • 3% nitrogen • Water & sulfuric acid clouds • Temperature:860°F

  13. Carbon Dioxide

  14. Carbon Dioxide Levels Muana Loa Readings CO2 Levels Since 1958 370 350 CO2 (ppm) 330 310 40 30 20 10 0 420 370 320 CO2 (ppm) 270 220 Dome Concordia Vostok Ice Core 170 600000 400000 200000 0 Time (YBP)

  15. Worldwide Carbon Emissions Total Liquid fuel Solid fuel Gas fuel 8 7 6 5 Carbon (109 metric tons) 4 3 2 1 0 1750 1800 1850 1900 1950 2000 Year

  16. Annual Carbon Emissions Annual carbon emissions Atmospheric CO2 Atmospheric CO2 average 8 6 Carbon (109 metric tons) 4 2 0 1955 1965 1975 1985 1995 2005 Year

  17. Future Carbon Dioxide Levels • Increasing CO2 emissions, especially in China and developing countries • Likely to double within 150 years: • Increased coal usage • Increased natural gas usage • Decreased petroleum usage (increased cost and decreasing supply)

  18. Kyoto Protocol • Adopted in 1997 • Cut CO2 emissions by 5% from 1990 levels for 2008-2012 • Symbolic only, since cuts will not significantly impact global warming

  19. Past Temperatures

  20. Recorded Worldwide Temperatures Decreasing Flat 0.8 0.6 0.4 0.2 D Mean Temperature (°C) 0.0 -0.2 -0.4 -0.6 1880 1900 1920 1940 1960 1980 2000 Year

  21. Historic Los Angeles Temperatures Annual Temperatures Summer Temperatures Winter Temperatures 25 17 22 21 24 16 20 23 15 19 22 14 Temperature (°C) 18 21 13 17 20 12 16 19 11 15 18 10 1880 1900 1920 1940 1960 1980 2000 1880 1900 1920 1940 1960 1980 2000 1880 1900 1920 1940 1960 1980 2000 Year Year Year

  22. 2007 Temperature Changes Compared to 1951-1980 -3 -2.5 -1.5 -1 -.5 -.1 .1 .5 1 1.5 2.5 3.4

  23. Past Temperatures Measurement • Proxy – a method that approximates a particular measurement (e.g., temperature) • Ice cores • Pollen records • Plant macrofossils • Sr/Ca isotope data • Oxygen isotopes from speleothem calcite (stalactites and stalagmites)

  24. Temperature History of the Earth • Little ice age (1400-1840) – 1°C cooler • Medieval warm period (800-1300) – 1°C warmer than today • Cool/warm cycles occur ~1,500 years • Affect mostly Northeastern U.S. and North Atlantic • Mostly due to changes in thermohaline circulation  • Dramatic shutdown of thermohaline circulation occurred 8,200 years ago as a large lake in Canada flooded the North Atlantic

  25. Main Ocean Currents Adapted from IPCC SYR Figure 4-2

  26. Temperature History of the Earth • For the past 3 million years, the earth has been experiencing ~100,000 year long cycles of glaciation followed by ~10,000 year long interglacial periods • These climate periods are largely the result of cycles in the earth’s orbit – precession, obliquity, and eccentricity

  27. Orbital Parameters: Precession Perihelion Apehelion

  28. 22.5° 24.5° Orbital Parameters: Obliquity

  29. Apehelion Apehelion Perihelion Orbital Parameters: Eccentricity Maximum: 0.061 Minimum: 0.005 Not to scale! To Scale!

  30. Precession(22 ky) Obliquity(41 ky) Eccentricity(100 ky) Temperature Orbital Parameters & Earth’s Climate 1000 900 800 700 600 500 400 300 200 100 0 Age (kya)

  31. Temperature History of the Earth • For the past 3 million years, the earth has been experiencing ~100,000 year long cycles of glaciation followed by ~10,000 year long interglacial periods • Last ice age began to thaw 15,000 years ago, but was interrupted by the “Younger Dryas” event 12,900 years ago

  32. YoungerDryas Medieval Warm Ice Age Little Ice Age Younger Dryas Event -25 0.35 -30 0.30 -35 0.25 Snow Accumulation (m/yr) -40 0.20 Temperature (°C) -45 0.15 -50 0.10 -55 0.05 20 15 10 5 0 Age (kya)

  33. Younger Dryas Event -34 -8.0 YoungerDryas -35 -7.5 -36 -7.0 -37 -6.5 -38 -39 -6.0 d18O (Greenland) d18O (China) -40 -5.5 -41 -5.0 -42 -4.5 -43 -44 -4.0 16 15 14 13 12 11 10 Age (kya)

  34. Temperature History of the Earth Middle Pliocene (3.15 to 2.85 million ya) • Temperatures: 2°C higher than today. • 20°C higher at high latitudes • 1°C higher at the Equator • Sea levels were 100 ft higher • Causes • CO2 levels that were 100 ppm higher • Increased thermohaline circulation

  35. Temperature History of the Earth Eocene (41 million years ago) • Opening of the Drake Passage (between South America and Antarctica). • Increased ocean current exchange • Strong global cooling • First permanent glaciation of Antarctica ~34 million years ago

  36. Temperature History of the Earth Paleocene Thermal Maximum (55 mya) • Sea surface temperatures rose 5-8°C • Causes • Increased volcanism • Rapid release of methane from the oceans

  37. Temperature History of the Earth Mid-Cretaceous (120-90 mya) • Much warmer • Breadfruit trees grew in Greenland • Causes • Different ocean currents (continental arrangement) • higher CO2 levels (at least 2 to 4 times higher than today, up to 1200 ppm)

  38. Recent Temperature Changes

  39. “Hockey Stick” Controversey 0.6 Direct temperature measurements Mann et al. 1999 0.4 0.2 0 Temperature Change (°C) -0.2 -0.4 -0.6 -0.8 1000 1200 1400 1600 1800 2000 Year

  40. Is the Hockey Stick Correct? 2 Mann et al. 1999 Esper et al. 2002 1 0 Temperature Change (°C) -1 -2 800 1000 1200 1400 1600 1800 2000 Year

  41. Mann et al. 1999 Esper et al. 2002 Moberg et al. 2005 Mann et al. 2008 Is the Hockey Stick Correct? 0.4 0.2 0.0 -0.2 -0.4 Temperature Change (°C) -0.6 -0.8 -1.0 -1.2 0 400 800 1200 1600 2000 Year

  42. “2:1 chance of being right” “high level of confidence” U.S. National Academy of Sciences: June 2006 0.6 0.4 0.2 0 Temperature Change (°C) -0.2 -0.4 -0.6 -0.8 1000 1200 1400 1600 1800 2000 Year

  43. Atmospheric Temperatures Troposphere Stratosphere 0.8 1.5 0.6 1.0 0.4 0.5 0.2 Temperature Cgange (°C) 0.0 0.0 -0.2 -0.5 -0.4 -0.6 -1.0 1980 1990 2000 1980 1990 2000 Year Year

  44. CO2 Concentration Vs. Temperature 370 320 31 30 SST (°C) Tropical Pacific CO2 (ppm) Antarctica 270 29 28 220 27 26 170 25 600000 400000 200000 0 Time (YBP)

  45. Consequences of Global Warming

  46. Global Warming Primarily Impacts the Northern Hemisphere Northern vs. Southern Latitude Land vs. Ocean 1.0 Land Ocean Northern Hemisphere Southern Hemisphere 0.8 0.6 0.4 0.2 Temperature Change (°C) 0.0 -0.2 -0.4 -0.6 1920 1960 2000 1920 1960 2000 Year Year

  47. 2007 Temperature Changes Compared to 1951-1980 -3 -2.5 -1.5 -1 -.5 -.1 .1 .5 1 1.5 2.5 3.4

  48. Ice Sheets Melting? • GRACE (gravity measured by satellite) found melting of Antarctica equivalent to sea level rise of 0.4 mm/year (2 in/century) • Zwally, 2005 (satellite radar altimetry) • confirmed Antarctica melting • Greenland ice melting onexterior, accumulating inland(higher precipitation)

  49. Melting Glaciers – Mt. Kilimanjaro

  50. Changes in Antarctica Ice Mass 1000 800 600 400 200 Ice Mass (km3) 0 -200 -400 -600 2004 2003 2005 Year

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