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Global Warming

Global Warming. Is Human-Induced Climate Change Going To Destroy The World? Ok… that’s a bit dramatic. But, good questions are: What is the evidence for recent climate change? Do we need to worry about it – what are the consequences? What can we do about it?.

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Global Warming

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  1. Global Warming Is Human-Induced Climate Change Going To Destroy The World? Ok… that’s a bit dramatic. But, good questions are: What is the evidence for recent climate change? Do we need to worry about it – what are the consequences? What can we do about it? Data and diagrams from Richard Deem, Michael Mann, Lee Kump and the Intergovermental Panel on Climate Change

  2. History of Earth’s Atmosphere/Climate • Earth formed ~4.6 billion years ago • Originally very hot, probably molten, early impact forming the moon • Any early atmosphere removed by initiation of sun’s fusion reactions and solar wind • Granitic crust and liquid water was present by ~4.3 billion years ago (zircon dating) • However, much of Earth’s early history was erased during late heavy bombardment (~3.9 billion years ago)

  3. History of Earth’s Atmosphere/Climate • First life appeared by ~3.8 Ga • Photosynthesis began 3.5-2.5 Ga, clear evidence for significant oxygen in the atmosphere by 2.0 Ga • Photosynthesis introduced oxygen and removed carbon dioxide and methane (greenhouse gases) • Earth began current cycles of glacial and interglacial periods ~3 Ma

  4. Sun Solar Energy Solar Energy Earth’s Temperature

  5. Sun Solar Energy Radiative Cooling Earth’s Temperature

  6. Sun Solar Energy Radiative Cooling Earth’s Temperature

  7. Sun Solar Energy Radiative Cooling Earth’s Temperature

  8. Sun Greenhouse Effect

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

  10. Sun Venus Runaway Greenhouse Effect • 97% CO2 • 3% N2 • Water & sulfuric acid clouds • Temperature:860°F (hotter than Mercury which is nearest to the sun)

  11. 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)

  12. 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

  13. 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

  14. Future Atmospheric CO2 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)

  15. Kyoto Protocol • Adopted in 1997 • Cut CO2 emissions by 5% from 1990 levels for 2008-2012 • Really is symbolic only, since such levels of reduction will likely not significantly impact global warming

  16. Recorded Worldwide Temperatures 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

  17. 2007 Temperature Changes Compared to 1951-1980 -3 -2.5 -1.5 -1 -.5 -.1 .1 .5 1 1.5 2.5 3.4

  18. 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)

  19. 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 over ~1,500 years • Mostly due to changes in thermohaline circulation system of the ocean

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

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

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

  23. “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

  24. 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)

  25. Consequences of Global Warming: Primarily Impacts the Northern Hemisphere and Land Masses 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

  26. 2007 Temperature Changes Compared to 1951-1980 -3 -2.5 -1.5 -1 -.5 -.1 .1 .5 1 1.5 2.5 3.4

  27. Consqeuences of Global Warming: Ice Sheets Melting? • GRACE (gravity measured by satellite) found melting in 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) • And - Glaciers are retreating all over the world.

  28. Consqeuences of Global Warming: Rise in Sea Levels? • Present rate is 1.8 ± 0.3 mm/yr (7.4 in/century) • Accelerating at a rate of 0.013 ± 0.006 mm/yr2 • If acceleration continues, could result in 12 in/century sea level rise • Scenarios claiming 1 meter or more rise are probably unrealistic

  29. Consqeuences of Global Warming: 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 • Summary – most studies suggest ~4°C over the next century

  30. -50 -20 -10 -5 5 10 20 50 Potential Worldwide Precipitation Changes

  31. Mitigation of Global Warming? • Conservation • Reduce energy needs • Recycling • Alternate energy sources • Nuclear • Wind • Geothermal • Hydroelectric • Solar • Fusion?

  32. Conclusions • Global warming is happening • Most warming is probably the result of human activities – but this is still under debate • There will be positive and negative (mostly) repercussions from global warming • The costs to mitigate global warming will be high – are they worthwhile?

  33. Extra slides 2010 beyond this point

  34. 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

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

  36. YoungerDryas Medieval Warm Ice Age Little Ice Age Younger Dryas Event – Greenland Data -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 (ka)

  37. 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

  38. 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

  39. “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

  40. Global Temperature Change Changing Sea Levels 20 10 0 Relative Sea Level (cm) -10 Amsterdam, Netherlands Brest, France Swinoujscie, Poland -20 1700 1750 1800 1850 1900 1950 2000 Adapted from IPCC SYR Figure 2-5

  41. Sea Levels for 450,000 Years 31 20 0 30 -20 29 -40 Sea Level (m) 28 SST (°C) Tropical Pacific -60 27 -80 26 -100 -120 25 450 400 350 300 250 200 150 100 50 0 Time (Ka)

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