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GLOBAL CHANGE

GLOBAL CHANGE. GLOBAL CHANGE. Changing faster today than at any other time Cause – human activity (anthropogenic). GLOBAL CHANGE. Deforestation. GLOBAL CHANGE. Greenhouse Gases & Greenhouse Effect. GLOBAL CHANGE. Destruction of Ozone Layer. GLOBAL CHANGE. Loss of Biodiversity.

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GLOBAL CHANGE

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  1. GLOBAL CHANGE

  2. GLOBAL CHANGE • Changing faster today than at any other time • Cause – human activity (anthropogenic)

  3. GLOBAL CHANGE • Deforestation

  4. GLOBAL CHANGE • Greenhouse Gases & Greenhouse Effect

  5. GLOBAL CHANGE • Destruction of Ozone Layer

  6. GLOBAL CHANGE • Loss of Biodiversity

  7. GLOBAL CHANGE • Global Warming

  8. GLOBAL CHANGE • Global Warming

  9. THREE MAJOR THEMES • Global Environmental Issues • Need to be informed to make intelligent decisions • Global Change in the Past • Need to understand how planet was changing before humans • Global change can occur on short (1000’s years) or long (millions of years) time scales • The Earth System • Different components of Earth interact in response to forcings (internal and external influences)

  10. THE EARTH SYSTEM

  11. GLOBAL CHANGE – SHORT TIME SCALE • Global warming – an increase in Earth’s surface temperature caused by industrial and agricultural activities • Release gases that increase greenhouse effect • Intergovernmental Panel on Climate Change (IPPC) – 2007 • “Warming of the climate system is unequivocal, as it is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”

  12. Measuring Atmospheric CO2 – The Keeling Curve

  13. Measuring Atmospheric CO2 – The Keeling Curve • 1958 – 315 ppm • 2008 – 386 ppm • 1 cc of air = 2.7 x 1019 molecules • 1ppm concentration = 2.7 x 1013 molecules • Most increase due to combustion of fossil fuels (coal, oil, natural gas) • Tropical deforestation also contributes • Trend of increasing atmospheric CO2 is real

  14. Climate Proxy Data

  15. Measuring Atmospheric CO2 – Ice Cores • Use air bubbles trapped in polar ice • Matches direct measurement well – reliable technique for determining long-term CO2 concentrations • Pioneer Effect • 1800-1850 (before Industrial Age) • Increased CO2 due to deforestation of American West

  16. OTHER GREENHOUSE GASES • Methane (CH4) & Nitrous Oxide (N2O) – from agriculture • CFCs (Chlorofluorocarbons) – destroy stratospheric ozone too • HUMANS HAVE ALTERED EARTH’S ATMOSPHERE

  17. SURFACE TEMPERATURE • Global Mean Surface Temperature • increased 0.8 ℃ since 1900

  18. NECESSITIES • Understand the past in order to predict the future • Little Ice Age (1500-1850) • Understand the whole Earth system in order to correctly interpret the changes that are occurring • Sulfate aerosols • Understand the time scales on which global change occurs • Sulfate aerosols removed in weeks, CO2 stays for centuries

  19. CRYOSPHERE CHANGES • Warming at the poles could raise sea level • Greenland ice cap – sea level increase 6 meters (20 feet)

  20. CONSEQUENCES OF GLOBAL WARMING • Rise in sea level • 10 cm in last 100 years • Thermal expansion • Melting ice • Impact agriculture • Decreased soil moisture • Spread of tropical pests • Stronger hurricanes • Earth has been significantly warmer in the past – past is the key to the present

  21. OZONE DEPELTION • 1985 – discovery of ozone hole above Antarctic • 1975-1990 – ozone dropped by half (October) • Inverse relationship between ozone and ClO (chlorine monoxide)

  22. DEFORESTATION ANDLOSS OF BIODIVERSITY • Humans have been altering the land surface for 10,000 years • Tends to reduce complexity of landscape • Reduces biodiversity • Change in land can cause species unable to move ore adapt to become extinct • Genetic information lost • Currently, greatest loss of species is in the tropical rainforests • Rainforests most biodiverse habitats • Rainforests disappearing the most

  23. OF MOST CONCERN? • Ozone Depletion? • Omit CFCs - recovery in 50-150 years • Increased CO2? • Stop CO2 emissions – recovers in 1-2 million years • Loss of Biodiversity? • Mass extinction – never recovers completely

  24. PAST GLOBAL CHANGE • Glacial-Interglacial cycles • Mass Extinctions • Solar Luminosity Change

  25. HOW LONG IS LONG? • The Geologic Time Scale – • Divisions based on appearance/disappearance of organisms • Earth is 4600 million years old (4.6 billion) • Most of Earth time before animals with preservable hard parts appeared • Cambrian 544 mybp • Precambrian 544-4600 mybp

  26. THE GEOLOGIC TIME SCALE

  27. Ice-Core Temperature Record • Antarctica • Vostok and Dome C • 800,000 years • CO2 concentrations • Temperature • Based on deuterium • Glacial/Interglacial Periods • Last Ice Age ended 11,000 years ago

  28. Dome C Data

  29. ICE CORE RESULTS • Surface Temp , CO2 & CH4  • associated with interglacial periods • 21,000-11,000 ybp & 140,000-130,000 ybp • Why would CO2, CH4 & temperature co-vary? • Greenhouse Effect • Change in deep ocean circulation due to change in climate (brings more CO2) • Atmospheric CO2 affects climate and climate affects atmospheric CO2

  30. MASS EXTINCTION • 65 mybp • Dinosaurs extinct • 60-80% of marine species extinct • Numerous terrestrial organisms • WHY?

  31. K-T Mass Extinction • Clay layer at K-T boundary • Walter & Luis Alvarez • Use iridium to determine rate of clay deposition • Iridium 100 x higher than expected • Iridium uncommon on Earth – reasoned that it came from the impact of a large extraterrestrial object

  32. MASS EXTINCTIONS • The Earth system has recovered from large shocks in the past • Recovery is slow • Recovery generates a modified Earth

  33. SOLAR LUMINOSITY • As the sun ages and uses up its hydrogen fuel – its luminosity (brightness) increases • 4,600 mybp Sun was 30% dimmer (less luminous) • Luminosity has increased slowly, then rapidly • Currently brightness increases 1% /100 x 106 years • In 5,000 my – 2-3 times brighter than now • Early Earth colder (if other factors constant) • Ocean should have been frozen – BUT NO • 3.8 bya – sedimentary rocks • 3.5 bya – organisms • Faint Young Sun Paradox – solution? • Higher levels of Greenhouse gases in early atmosphere

  34. SOLAR LUMINOSITY

  35. GAIA HYPOTHESIS • James Lovelock & Lynn Margulis • Earths is a self-regulating system in which the biota play an integral role • The biota manipulate the environment for their own benefit, or by optimizing the conditions for life, for the benefit of all living organisms • Life itself is responsible for maintaining the stability of Earth’s climate • Climate stability implies self-regulation • Biotic feedbacks (Gaia Hypothesis) • Abiotic feedbacks (carbonate-silicate geochemical cycle)

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