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Climate change – Natural Causes
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  1. Climate change – Natural Causes CATASTROPHIC Volcanic Eruptions Meteorite Impacts REGULAR Orbital Variation, Solar Cycles & Cosmic rays Tectonic Shift

  2. Volcanic Explosivity Index Volcanoes have the capability of throwing cubic kilometers of ash and debris into the atmosphere which can significantly alter the climate for years at a time– this is measured by the Volcanic Explosivity Index (VEI) Source: US Geological Survey: http://volcanoes.usgs.gov/images/pglossary/vei.php

  3. Volcanic Eruptions Short eruptions can influence climate patterns for years due to the outpouring of gases and ash Droplets containing about 75 percent sulfuric acid can linger as long as three to four years in the stratosphere. Major eruptions alter the Earth's radiative balance because volcanic aerosol clouds absorb terrestrial radiation, and scatter a significant amount of the incoming solar radiation, an effect known as "radiative forcing" that can last from two to three years following a volcanic eruption. Source: NASA: http://earthobservatory.nasa.gov/Features/Volcano/

  4. The Year Without a Summer • Mount Tambora, Indonesia erupted in April 1815 with a rating of seven on the Volcanic Explosivity Index • The 1815 eruption of Tambora was the largest volcanic eruption in recorded history. The explosion was heard 2,600 kilometres away, and ash fell at least 1,300 kilometres away • An aerosol of sulphuric acid circled the globe and blocked a large proportion of the sun’s energy from reaching the earth. This was called the sulfate aerosol veil. • In 1816, global temperatures fell dramatically: • in June – 30 cm of snow fall was recorded in Quebec City • Drought conditions were reported in July and August as rainfall patterns changed. • Widespread crop failure due to lack of direct sunlight in Europe and North America created famine. • Early frosts in August and September damaged the few crops which did grow • Significant livestock deaths were recorded in North America in the winter of 1816-17 due to lack of food for the animals. • Source: Wikipedia: http://en.wikipedia.org/wiki/Year_Without_a_Summer

  5. Volcanic Activity Mount Pinatubo, Philippines - 1991 The powerful eruption of such an enormous volume of lava and ash injected significant quantities of aerosols and dust into the stratosphere. Sulfur dioxide oxidized in the atmosphere to produce a haze of sulfuric acid droplets, which gradually spread throughout the stratosphere over the year following the eruption. The total mass of SO2 of about 17 million tons being ejected. This very large stratospheric injection resulted in a reduction in the normal amount of sunlight reaching the Earth's surface by roughly 10%. This led to a decrease in northern hemisphere average temperatures of 0.5–0.6 °C and a global fall of about 0.4 °C At the same time, the temperature in the stratosphere rose to several degrees higher than normal, due to absorption of radiation by the aerosols. The stratospheric cloud from the eruption persisted in the atmosphere for three years after the eruption. Source: US Geological Survey: http://pubs.usgs.gov/fs/1997/fs113-97/

  6. Meteorites • Large meteorite impacts have been noted in the geological records • Depending on their size, their impacts on climate can be larger than volcanoes • An example of one huge impact is located in the Yucatan peninsuala in Mexico called the Chicxulub crater – thought to have been formed 65 Million years ago • The crater is more than 180 kilometers in diameter, the impacting meteor that formed the crater was at least 10 km in diameter. • The meteor triggered an extinction level event as debris would have been thrown into the atmosphere and blocking sunlight from reaching the surface. Almost all plant and animal life was thought to have been extinguished by this event. • A layer of Iridium rich sediment is seen in the geologic record around the world confirming the impact. http://www.metacafe.com/watch/2070635/video_of_meteor_crashing_in_canada_meteorite_impact_reformulated_earths_crust/

  7. Milankovitch Cycles Milutin Milankovitch (1920) first proposed that glacial-interglacial cycles were controlled by the amount and distribution of radiation received from sun. Milankovitch argued that different periods of major glaciations were initiated by changes in Earth's orbital parameters of: Eccentricity -100 000 year cycle Axial Tilt (obliquity) – 41 000 year cycle Precession or Wobble – 21 000 year cycle 7

  8. Eccentricity • Eccentricity is the change in the shape of the Earth's orbit around the sun. • There is only about a 3% difference in distance between the time when we're closest to the sun (perihelion) and the time when we're farthest from the sun (aphelion). • Perihelion occurs on January 3 and at that point, the earth is 146 million km away from the sun. • At Aphelion, July 4, the earth is 156 million km from the sun. • Over a 100,000 year cycle, the earth's orbit around the sun changes from a thin ellipse (oval) to a circle and back again. http://oceanworld.tamu.edu/students/iceage/iceage2.htm

  9. Obliquity • The angle of the Earth's axial tilt, or obliquity, varies with respect to the plane of the Earth's orbit. • These slow 2.4° obliquity variations take approximately 41,000 years to shift between a tilt of 22.1° and 24.5° and back again. • Less of an angle than our current 23.45° means less seasonal differences between the Northern and Southern Hemispheres while a greater angle means greater seasonal differences (i.e. a warmer summer and cooler winter). • The tilt is in the decreasing phase of its cycle, and will reach its minimum value around the year 10,000 • This trend would tend to make winters warmer and summers colder

  10. Precession • Precession operates on a 21 000 year cycle; also referred to as wobble. • 12,000 years from now the Northern Hemisphere will experience summer in December and winter in June because the axis of the earth will be pointing at the star Vega instead of it's current alignment with the North Star or Polaris. • This seasonal reversal won't happen suddenly but the seasons will gradually shift over thousands of years. • Precession occurs due to the tidal forces generated by the gravitational attraction of the moon and sun combined on the Earth.

  11. Schwabe Cycle Cosmic rays cause high level clouds to form => cooling “active” sun produces more solar wind that deflects cosmic rays => warming cycles see combinations of solar intensity overlaid with changes in cosmic ray concentration as we move around the galaxy 11

  12. Sunspot Observations The Maunder and Dalton Minimum resulted in a cool period in global temperature

  13. Schwabe Cycle Sun has direct relationship to temperature on both long term and short term scales 13

  14. Solar Activity Cycle

  15. Tectonic Shift The continental land masses have moved throughout time. At one time, all of the continents were together in a single land mass, named Pangea, that fractured, forming oceans between them. As continents changed position based on latitude, their individual climates would obviously change accordingly. The relative longitudinal positions of the continents also has an impact on global climate however. As Africa moved north into Europe, it forced ocean currents to divert around it, driving these warm bodies into the cooler polar regions Youtube video: http://www.youtube.com/watch#!v=NYbTNFN3NBo&feature=related 15

  16. Tectonic Shift Continents had been arranged so warm equatorial currents flow freely. Equatorial current is heated more as it circumnavigates the Earth more than once. North & South flowing currents diverging from it are warmer. 16

  17. Tectonic Shift Fossil forests similar to those found in the Georgia today have been found in the Eocene sediments of Axel Heiberg Island. 17

  18. Tectonic Shift Present Conditions Equatorial current closed off 3 mya Gateways at high latitude allow circumpolar currents to pass. Circumpolar currents insulate polar continents from warmer seas & cause polar temps to drop. 18

  19. Orogenesis • Tectonics also cause mountain formation • Present Monsoons are a geologically NEW addition to climate there • Mountains cause rain, plateaus dry conditions • N.A. forests and prairies result 19