Section 4 Professor Donald McFarlane

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1 Carbon cycle Present in atmosphere in low concentrations Autotrophs incorporate it into organic matter via photosynthesis Section 4 Professor Donald McFarlane Lecture 23 and Climate Carbon Cycle Respiration and decomposition of plants recycles a similar amount back into the atmosphere as CO 2 Carbon is incorporated into shells of marine organisms eventually forming limestone deposits Volcanoes and hot springs release large amounts Burning fossil fuels is adding CO 2 and particulate matter to the atmosphere 2 Atmosphere Decomposition and respiration Soil Deposits of fossil fuels coal, oil, and natural gas Photosynthesis Plants Deation Rocks Burning of fossil fuels Algae Atmospheric CO 2 Biological and chemical processes Sedimentation forms fossil fuels. ion (ppm) CO 2 concentrati Temperature vari iation (ºC) Year 4 1

2 Greenhouse effect Solar radiation passes through the atmosphere and heats the Earth s surface Energy radiated from the Earth back into atmosphere Atmospheric gases absorb much of this energy and reradiate to the Earth s surface increasing the temperature further Without this effect, life would not exist on Earth Caused mainly by water vapor, carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons 5 Sunlight Atmosphere Heat Carbon dioxide Heat 6 Oxygen isotopes in foraminiferans 7 8 2

3 Oxygen isotope Record (deep ocean cores) Sea level Curve 9 10 Global warming Human activities increasing the greenhouse effect All greenhouse gases have increased in atmospheric concentrations since industrial times CO 2 has a lower warming potential per unit of gas but its concentration in the atmosphere is much higher Anticipated changes in global climate will occur too rapidly for normal evolutionary processes to compensate Climatic zones may shift faster than trees can migrate via seed dispersal resulting in extinction Sugar Maples Current range (blue) predicted range (red) under 2x CO

4 Atmospheric circulation Differences in temperature occur due to latitudinal variations in incoming solar radiation In higher latitudes the sun s rays hit the Earth obliquely and are spread out over more of the planet s surface than they are in equatorial areas Generally, temperature increases as the amount of solar radiation increases Global patterns of atmospheric circulation and precipitation are influenced by solar energy Hadley proposed model based on one large convection cell in each hemisphere Based on warmth at equator causing air to rise and flow north and south toward poles Air would cool and fall, flowing back to the equator 15 Coriolis effect adds in effect of Earth s rotation Deflects surface flow westward 3 cells in each hemisphere Hadley cell nearest equator Polar cell nearest poles Ferrell cell in between Major biomes determined by temperature differences and wind patterns rises rain Ferrell cell Dry air falls desert Hadley cell rises rain Dry air falls desert rises rain Doldrums Polar cell Westerlies Subsidence zone Northeast trades Polar front ITCZ Southeast trades Subsidence zone Westerlies Polar front Cold, dry air falls Polar cap 16 60ºN 30ºN 0º 30ºS 60ºS Polar cap Cold, dry air falls 4

5 Polar high sparse precipitation in all seasons Arctic tundra Taiga Subpolar low ample precipitation in all seasons 60ºN Temperate and grassland Dry air Winter wet, summer dry Subtropical high dry in all seasons Summer wet, winter dry Abundant Equatorial low Precipitation (ITCZ) in all seasons Summer wet, winter dry Subtropical high dry in all seasons Winter wet, summer dry Subpolar low ample precipitation in all seasons Polar high sparse precipitation in all seasons 30ºN Desert Equator rain 0º Desert 30ºS 60ºS (a) Rain shadow Elevation and other features can affect climate Adiabatic cooling increasing elevation leads to 10 C drop for every 1,000m Rain shadow warm, moist air flows up mountain and cools releasing precipitation, leeward side allows drier air to descend forming area where precipitation noticeably less ipitation (cm) Annual preci Temperate rain Temperate rain 30 N Equator 30 S Tundra Taiga Temperate grassland Cold desert Average temperature ( C) grassland Hot desert rain Temperate rain and taiga Temperate grassland (savanna) Temperate grassland (prairie) Hot desert Cold desert Tundra Mountain ranges Polar ice cap 20 5

6 Together with rotation of the Earth, winds also create ocean currents