Sarah RoseCH 12 LONG TERM CLIMATE REGULATION Faint Young Sun Paradox-sun puts out 30% less energy during the early Solar System -increasing brightness ever since, increasing present day luminosity-most likely solution to paradox is the greenhouse effect, enough greenhouse gases would warm Earth enough to stay above freezing Energy Balance with Faint Sun-Global average surface temperature-Energy in from sun-Energy out from black body radiation from top of atmosphere -Surface temperature warmer then top of atmosphere due to green house effectBased on assumptions we gather Earth was frozen 2 Gyr-reality=stromatolites show photosynthesis by 3.5 Gyr-conclusion=earth not completely frozen at all times 2Gyr agoCO2 most likely warmed Earth-smaller continentsless weatheringless CO2 removalmore CO2-impact degassing of planetismals and volcanoesmore CO2-weathering of seafloorless CO21,000 times the current amount of CO2 would have beenneeded to keep the Earth from freezing (relatively small incomparison to the amount of carbon in total carbon cycle)Methane (in early atmosphere)-prior to formation of life impact degassing produced CH4-reaction of rocks on seafloor produce CH4-estimate concentration prior to life 10-100 ppm, today 1.75ppm-earliest organisms methane producing bacteria (methanogenic)-1000 ppm 3.8-2.3 Gyr agoNegative feedback involving methanogenic bacteria and haze production could have controlled Archean climate (2.5-3.8 Gyr)Tillites, mixture of cobbles, pebbles, sand, and mud packed together to form rocks, mix of sediments pushed together by glaciersMoraines, debris carried by glaciers as they move and deposited in piles of rubble, hills created by glaciers pushing dirt and rocks1Glacial striations, parallel scratches on rocks formed when moving glaciers drag other rocks across their surface, gouges cut by rocks frozen in moving glaciersDropstones, misplaced chunks of rock that occur in finely laminated sediments Loess, fine-grained sediment produced by glacial abrasion and carried by widnGlaciations-Mid Archean (2.9 Gyr ago) -atmospheric O2 just increased before this time and went back down which could have destroyed the methane greenhouse-could have been presence of the organic haze (anti greenhouse effect)Huronian, rise of O2 around 2.4 Gyr ago would have eliminated most of the methaneCarbon-silicate cycle ended glaciations-CO2 outgassing from volcanoes stays constant -CO2 removal by silicate weathering in warm climates, removal slows in cold climates-If cold CO2 builds up, warming climate back upSnowball Earth -late Proterozoic 0.75-0.60 Gyr-glaciers on all continents/equator-low latitude glaciation called snowball Earth -sea ice 1 km thick, impenetrable by sunlight -photosynthetic organisms survived either by:-slushball Earth (patches of unfrozen spots on Earth)-life survived in geothermally heated zones (mid ocean ridges)-ice not uniformly thick, thin enough in some areas for light to penetrate Formation -theory 1, CO2 concentrations drawn down to low values, land situated in the tropics, high silicate weathering, lower CO2-theory 2, O2 increased, methane flux may have gone down, ice sheets creep to loweraltitudes, snow ice albedo positive feedback because so strong the system back unstable (ocean freezes to equator)2once surface froze, no more silicate weathering, volcanic CO2 begins to accumulate and in about 10 Myr CO2 reaches 0.1 bar (300x current level) and ice meltsCarboniferous cooling, time of formation of fossil fuels, carbon burial rate doubled (decrease in CO2)Mesozoic warm-time of dinosaurs, ferns and alligators in Siberia-cause by high CO2 levelsCenozoic cooling-formation of Himalayas provides fresh surface for silicate weatheringCO2 levels reduceclimate cools-50Mys-present -period of evolution of mammals-old world monkeys evolved 20 Myr agoSUMMARY-periods of warmth and glaciation over Earth’s history3-Greenhouse warming kept Earth from freezing during entire early period of Faint Sun-Snowball Earth periods = times where greenhouse gases dropped-Greenhouse gas levels are the main control of climate in Earth’s historyCH 13 BIODIVERSITY THROUGH EARTH’S HISTORYEvolution, the change from one generation to the next of inherited characteristics ofa population of organisms -mutations enhance variability-most mutations are detrimental (reduce change of survival) -beneficial mutations are called adaptations Natural selection is the process by which adaptations are passed on to offspring because the organism has a higher chance of survival/reproduction Extinction is the loss of all individuals within a speciesOrigination is the process by which a new species can form if a population becomesisolated and natural selection results in changes that prevent interbreeding Rate of change in # of species = origination rate – extinction rateOrigination rate has slightly exceeded extinction rate on long term scale (3.5 billion years)Fossils-shelled marine organism appear 500 million years ago-incomplete fossil recordsMorphology, organisms that can interbreed are classified as species, but fossils cannot so we use similarities in morphology (body shape) to group themGlobal biodiversity has over all increased over the last 500 million years (fluctuations and uncertainties) Significant bias in fossil record, youngest rocks have increased areas exposed to the surface and volume whereas older rocks have been subject to erosion, potentially reducing amount of (older) fossils we find“Pull of the recent” refers to a higher abundance of modern rocks and outcrops which artificially enhance species biodiversity Taxonomy, is the systematic organization ofliving or fossil organisms into a hierarchyGenus and above have much less bias in fossilrecord (regarding Graph)Trends are not accurate 4Figure are still missing extinction at end of Cretaceous (K) and limp fossils into ‘bins’of 11 million years (misses key extinctions)Large increases in biodiversity occur between Cambrian (Cm) and Ordovician (O) because shelly marine organisms first appear Large decrease of biodiversity (mass extinction) occur at end of Permian (P) and Triassic (Tr) and Cretaceous (K)Mass extinctions are when 50% or more of genera (multiple genus) got extinct-largest know mass extinction occurred 252 million years ago(P) up to 95% of all species might have gone extinct due to massive volcanic eruptions in Siberia may have breached a huge coal bed which released CO2, resulted in