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a global warning.docx

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Department
Life Sciences
Course
LIFESCI 2H03
Professor
Luc Bernier
Semester
Winter

Description
February 4 , 2013 Life Sci 2H03: Environmental Life Sciences A Global Warning? Introduction - 125thousands years ago: earth is watery, high seas - 55mya: temperature rockets - 250mya: explosion of GHG triggers global warming and wipes out 95% of species - 650mya: earth is covered in ice, thick ice sheet, 40 F below zero, ocean freezed over 650 Mya - death valley Nevada - dropstones: bolders that don’t belong in the terrain of death valley Nevada  glacial dropstone  boulder carried by ice sheet  dating age to 650 mya  because structure and magnetic properties: originated miles away  ice melts and rock drops in new location - drop stones found all over the planet at this time indicating ice was covered in snow - what triggered ancient big freeze which lasted to 10 million years - most of the land is arranged around equator - warm temperature and precipitation, GHG level drops and planet begins to cool - snows reflection is critical for the climate of the surface: most of the sunlight was reflected so the earth remained cold = albedo - dark ocean = low albedo absorbs suns energy - snow = high albedo reflects sunlight cooling the planet - ice sheets reflect the suns warmth back in to space, decrease temperature and ice continues to form - meter thick floating pack ice at equator at which point the food supply would be gone - unlikely that planet will be locked in snowball earth again - albedo effect is always active and is now pushing our climate in the opposite direction - today we have a decrease in the snow cover, which lowers the albedo - after 10my snowball comes to an end due to volcanic eruptions emitting GHG into the atmosphere warming the earth - climate stabilizes and life flourishes 250 Mya - 95% of species are extinct - climate rockets - warming - South Africa - Before the mass extinction: lush plane flourishing with life – vegetation, animals, lakes - Largest reptiles, Gorganopses, evolved:  Were the top predators  Proof of their extinction lies in the mountain basins  Layers of rocks were built up gradually over time - biggest mass extinction event throughout the history of earth - division between the grey and white rocks: were all the species were wiped out - this line tracks around the entire world: same extinction event - answer lies in Siberia:  moulton rocks = Siberian traps  layed down 250 million years ago  lava came from beneath the earth surface: flood basalts  flood basalt eruptions and fire fountains of lava eruption for around 1 million years covering an area 5 times the size of Texas with lava a mile deep  greenhouse gases  produced global warming as one of the main gases  temp increased 10 C worldwide - lungs of the plants demonstrate high levels of CO : ap2roximately to about 10 times the amount from today - number of fossil breeding pores in plants decrease as CO incre2ses - CO 2ncreased by 700% trapping warmth - Global temp rose 18 F o - Could human activity today push CO to th2se levels that triggered the mass extinction o - If you double carbon dioxide you get an increase in 5 or 6 C - Planet slowly cools, new life forms flourish 55 Mya - temp 20 higher than it is today - Arctic - CO 2s not responsible - Scientist look into the ocean core looking for clues - Sediment cores - By using radioactive dating they attain the 55 million year mark - Find fossilized remains of a fern which can only flourish in warm waters indicating that the artic ocean would have been a warm tropical ocean 55 million years ago - Artic was tropical to temperate rain forest - Global temperatures were 20 F higher than today - What transformed the artic into the everglades:  Volcanic eruptions that blast GHG into the atmosphere  Temps rise but this alone is not enough - ocean of the coast of Santa Barbara, California  methane bubbles leaking from cracks: potent greenhouse properties  bacteria produce methane from dead plankton  some freezes into methane hydrate lies on ocean floor: pressure and cold water  goes from solid to gas  methane is more powerful than CO 2  can spike the temperature  volcanic activity could have warmed the ocean melting the frozen methane gas and releasing it into the atmosphere - today, warming oceans could have the same consequences - off the coast of the Florida Keys – how fast our water is warming  using corals to determine temperature  corals are made up of millions of sea creatures  secrete carbon calciate layers build up  the warmer the ocean, the faster the calcium carbonate is produced  area between each marked line indicates growth within a year  compare width of growth band  bands 1975 are larger than those of the 1700s  the wider the band the more coral has grown and because they grow faster when the seas are warmer we can conclude that ocean temperatures have been rising  coral samples show the same pattern of faster growth rate  corals from great barrier reef indicate increase growth rate indicating global response  ocean temp increased by 2 F in the past 100 years  increase of a few degrees could release frozen methane - 2002: biggest methane release ever seen in the Santa Barbara channel  divers inject green die in the rising bubbles of gas revealing a massive methane release on the surface  only a fraction of what could be released  methane is also highly flammable, an electric storm could ignite the methane and cause an explosion - these temps lasted for 200 thousand years then temperatures began to drop and polar ice caps began to reappear 125 000 Years Ago - ice sheets are on the retreat - sea levels rise sharply - oceans submerge the continents - Florida:  Cory walls are ancient remains of a coral reef  These corals only lives between 10 and 20 feet below water about 125 000 years old  Sea level probably ten feet higher than now  Melting ice caps must have pushed sea levels higher  9 F hotter than today - polar ice caps had grown and melted repeatedly over the past 2 million years:  gravitational pulls of sun, moon and planets, change the shape of the Earth’s orbit around the sun occurring in regular cycles which impacts the amount of sunlight reaching Eart
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