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Climate Change © 2014 Pearson Education, Inc. Earth’s Climate System • Climate – long-term atmospheric conditions in a region • Different from weather! • Earth’s climate includes interactions of: – – – – – Atmosphere Hydrosphere Geosphere Biosphere Cryosphere © 2014 Pearson Education, Inc. • Climate scientists use 3 methods: • Look at geologic records and fossil records • Build computer models • Closely monitor Earth’s current vital signs © 2014 Pearson Education, Inc. Determining Causes of Earth’s Climate Change • Paleoclimatology • Proxy data – indirect evidence using natural recorders of climate variability – – – – – – Sea floor sediments Coral deposits Glacial ice rings Tree rings Pollen Historical documents © 2014 Pearson Education, Inc. Proxy Data – Ice Cores © 2014 Pearson Education, Inc. Natural Causes of Climate Change • Solar energy changes – Variable energy from the Sun over time – Sunspots – cooler, episodic dark areas on Sun – Faculae – bright spots on Sun • Variations in Earth’s orbit • Volcanic eruptions • Movement of tectonic plates • Can change ocean circulation © 2014 Pearson Education, Inc. Natural vs. Human Caused Climate Change • Scientific consensus of large human contribution © 2014 Pearson Education, Inc. Atmosphere’s Greenhouse Effect • Global warming – increase in Earth’s global temperatures • Greenhouse effect – keeps Earth’s surface habitable – Incoming heat energy is shorter wavelengths – Longer wavelengths – some trapped, some escape, net warming effect © 2014 Pearson Education, Inc. Earth’s Heat Budget © 2014 Pearson Education, Inc. Greenhouse Gases • • • • Water vapor – Most important – 66–85% of greenhouse effect Carbon dioxide – Natural part of atmosphere – Released by living things as a result of respiration – However, levels have increased due to human activities – Burning of fossil fuels Methane – Second most abundant human-caused greenhouse gas – Great warming power per molecule – Landfill decomposition – Cattle – increased human population means increase cattle due to food source Other trace gases – Nitrous oxide, CFCs, ozone © 2014 Pearson Education, Inc. • How have humans caused increased carbon dioxide in the atmosphere? – Industrial Revolution • Led to burning of fossil fuels – Burning of fossil fuels is similar to cellular respiration – Humans have altered the carbon cycle – we are releasing more carbon dioxide into the atmosphere © 2014 Pearson Education, Inc. Atmospheric Carbon Dioxide © 2014 Pearson Education, Inc. Ice Core Data © 2014 Pearson Education, Inc. Changes from Global Warming • • • • • Melting glaciers and ice caps Shorter winters Species distribution shifts Global temperature rise Sea surface temperature increases © 2014 Pearson Education, Inc. Changes from Global Warming • The 8 warmest years have occurred since 1998 • Earth’s surface temperature has risen 0.8°C (1.4°F) in past 140 years. © 2014 Pearson Education, Inc. Changes from Global Warming Predicted Changes: • Earlier, hotter summers • Some areas could see more extreme winters • More severe droughts in some places, flooding in others • Retreat of mountain glaciers • Water contamination issues • Ecosystem changes and extinctions © 2014 Pearson Education, Inc. Scenarios for the Future © 2014 Pearson Education, Inc. Changes in the Oceans Increasing ocean temperatures • Sea surface temperatures risen mostly since 1970 • Deep waters showing increases © 2014 Pearson Education, Inc. Changes in the Oceans Increased hurricane activity • Warmer water fuels hurricanes • Severity of recent Atlantic hurricanes • Number of global tropical storms have not increased worldwide • Intensity of storms has increased – More Category 4 and 5 hurricanes © 2014 Pearson Education, Inc. Changes in the Oceans Changes in deep-water circulation • North Atlantic especially sensitive – Melting glaciers – Could change the way the ocean redistributes heat – Could change circulation patterns • Warmer surface waters © 2014 Pearson Education, Inc. Changes in the Oceans Polar Ice Melting • Arctic amplification • Loss of more than 2 million square kilometers (800,000 square miles) of Arctic sea ice in last decade • Loss of ice = enhanced warming due to lower albedo © 2014 Pearson Education, Inc. Changes in the Oceans Polar Ice Melting • Arctic ice melting affects polar bear survival. • Food sources are dwindling for human Arctic dwellers. – Marine species migration © 2014 Pearson Education, Inc. Changes in the Oceans Polar Ice Melting • Antarctica shrinking, glaciers thinning © 2014 Pearson Education, Inc. Changes in the Oceans Ocean acidity increase • Some atmospheric carbon dioxide dissolves in ocean water. – Acidifies ocean • Threatens calcifying organisms – – – – Coccolithophores Foraminifers Sea urchins Corals © 2014 Pearson Education, Inc. Organisms Threatened by Increased Marine Acidity • When we talk about ocean acidification, we don’t necessarily mean huge drops in pH – pH of ocean is ~8.6, slight decreases in pH could greatly affect organisms • pH is a measure of H+ in solution, on a log scale – Small decreases in pH can have a large effect on ocean organisms © 2014 Pearson Education, Inc. Changes in the Oceans • Rising Sea Level – already occurring • 2 main contributors: – Melting of land glaciers and ice caps – Thermal expansion of ocean water • Warmer water expands • Should we continue to build in some coastal areas? © 2014 Pearson Education, Inc. Rising Sea Level • Severely affect areas with gently sloping coastlines – U.S. Atlantic and Gulf Coasts • Models predict rise between 0.5 and 1.4 meters (1.6 and 4.6 feet) by year 2100 • Consequences: – Saltwater intrusion – Erosion – Increase storm damage – Loss of low lying areas – Loss of wetlands © 2014 Pearson Education, Inc. Changes in the Oceans Other predicted changes • Sound transmission in ocean • Reduced dissolved oxygen – marine dead zones • Does warmer or colder water hold more oxygen? • Change in ocean productivity • What could happen if the polar regions had less upwelling due to change in ocean circulation? • Marine organisms unable to adapt to temperature changes © 2014 Pearson Education, Inc. Reducing Greenhouse Gases • Human emissions contributing excessive CO2 • Global engineering – attempts to counteract human-caused climate change – Reducing sunlight reaching earth – Removing human-caused greenhouse gases © 2014 Pearson Education, Inc. Reducing Greenhouse Gases Ocean’s Role • Ocean’s biological pump – “Sink” for carbon dioxide – Pumps from surface to deep waters © 2014 Pearson Education, Inc. Reducing Greenhouse Gases • Ocean as thermal sponge – “heat sink” • Much of the surface of Earth is ocean, ocean water absorbs solar radiation – Unique thermal properties of water – Oceans absorb much heat without changing temperature – Oceans still warming © 2014 Pearson Education, Inc. Possibilities for Reducing Greenhouse Gases • Iron hypothesis – Fertilize ocean to increase productivity – Increase phytoplankton, increase carbon dioxide removal from atmosphere • Sequestering excess carbon dioxide in oceans © 2014 Pearson Education, Inc. Kyoto Protocol: Limiting Greenhouse Gas Emissions • International agreement – 60 nations • Voluntarily limit greenhouse gases • Even if gas emissions stabilize, Earth will continue to warm. – Commitment to warming • Human activities are altering the global environment. © 2014 Pearson Education, Inc. © 2014 Pearson Education, Inc.