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Climate Change & Ozone Loss

Climate Change & Ozone Loss. Chapter 20. Essential Question #1. How have the Earth’s temperature and climate changed in the past & how are greenhouse gases involved?. Past Climate Changes. Troposphere has experienced prolonged periods of: Global W arming (interglacial periods) &

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Climate Change & Ozone Loss

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  1. Climate Change & Ozone Loss Chapter 20

  2. Essential Question #1 How have the Earth’s temperature and climate changed in the past & how are greenhouse gases involved?

  3. Past Climate Changes • Troposphere has experienced prolonged periods of: • Global Warming (interglacial periods) & • Global Cooling (glacial periods) • For the last 12,000 years we have been in an interglacial period • Fairly stable for past 1000 yrs, begun rising during last century

  4. Average Global Temperature over the Past 900,000 Years 17 16 15 14 Average surface temperature (°C) 13 12 11 10 9 900 800 700 600 500 400 300 200 100 Present Thousands of years ago Fig. 16-2a, p. 369

  5. Temperature change over past 1,000 years Temperature change (C°) Year Fig. 20-2d, p. 465

  6. Average temperature over past 130 years Average surface temperature (°C) Year Fig. 20-2b, p. 465

  7. How do we know? • Past temperature measurements come from analyzing: • Radioisotopes in rocks and fossils • Ocean sediments • Tree Rings & Historical Records • Ice cores from ancient glaciers [CO2 & CH4]

  8. How Do We Know What Temperatures Were in the Past? • Ice Cores Teach Us About: • Troposphere Composition. • Temperature Trends. • Greenhouse Gas Concentrations. • Solar, Snowfall, and Forest Fire activity.

  9. Changes in [CO2] levels correlate closely with avg. global temp. for the past 160,000 years! • In 2005, an ice core showed that CO2 levels in the troposphere are the highest they have been in 650,000 years.

  10. 3 Major Factors Shaping Earth’s Climate • Solar energy • Greenhouse Effect • Oceans

  11. The Natural Greenhouse Effect • 4 Natural Greenhouse Gases • Water vapor (H20) • Carbon Dioxide (CO2)* • Methane (CH4)* • Nitrous Oxide (N2O) Absorb heat (infrared radiation) reflected from Earth’s surface & warm the troposphere

  12. Human Input of Greenhouse Gases • Burning fossil fuels • Adds CO2 & CH4 • Clearing & Burning Forests • Adds CO2 & N20 • Planting Rice & Using Inorganic Fertilizers • Adds N20 Figure 20-5

  13. Global CO2 Emissions China & the U.S. are the largest emitters of CO2

  14. Future of CO2 Emissions • Average concentration on CO2 rose from ~280 ppm at start of Industrial Revolution to 389 ppm in 2010. • If emissions continue at their current rate, levels could rise to 560 ppm by 2050 and 1,390 ppm by 2100. • Likely to cause major ecological and economic disruption. • Climate models indicate that 450 ppm may be a tipping point, that could set into motion large-scale climate changes for hundreds to thousands of years.

  15. Essential Question #2 & 3 What signs point to a warming troposphere? How is the earth’s temperature projected to change in the future and why should we care?

  16. Global Warming & Climate Change • Global Warming • Refers to temperature increases in the troposphere, which in turn can cause climate change • Global Climate Change • A broader term referring to changes in any aspects of the earth’s climate, including temperature, precipitation, & storm intensity patterns

  17. Findings from the IPCC • Intergovernmental Panel on Climate Change, IPCC • Formed by the United Nations & World Meteorological Organization in 1988 • A network of over 2,500 climate scientists and scientists in related disciplines from more than 130 countries • One of the longest and most thorough studies in the history of science • Based on over 29,000 sets of data and 18,000 peer reviewed publications

  18. Signs that Troposphere is Warming • According to the 2001 & 2007 IPCC Reports: • Earth’s lower atmosphere has warmed approx. 1° F (0.6° C) since 1980, due primarily to increased concentrations of greenhouse gasses • CO2, CH4 and N2O have risen sharply since 1861 (U.S. National Academy of Sciences) • Human activities played a major role in this warming, especially due to burning of fossil fuels & deforestation • Greenhouse gas emissions from human activities rose 70% between 1970 and 2009

  19. IPCC Report • 20th century was the hottest century in 1000 years • The first decade of this century (2000-2009) was the warmest decade since 1881 • Average surface temperature has risen by ~1.3° F betw. 1906 & 2005 • Glaciers and sea ice are melting and shrinking which exposes more dark land causing further warming

  20. Ice Melt

  21. IPCC Report • Permafrost is melting • releases CO2 and CH4 • Sea Levels are Rising • 7 in (19cm) last century

  22. IPCC Mathematical Models • Strong evidence to support that the warming observed in the “last 50 years is attributable to human activities” • 90-99% probability that mean surface temperature will increase by 4.5° – 9.7° F between 2000 and 2100 • Other scientific groups have reached similar conclusions

  23. IPCC: Future of Climate? If greenhouse gas concentrations continue to increase, the Earth is likely to experience rapid atmospheric warming and climate disruption during this century This would cause ecological, economic and social disruption

  24. Why should we be concerned? • Humans & biodiversity cannot adapt to rapid changes • Alter water availability • Alter biomes (& where crops can be grown) • Alter ocean currents / weather • Coastal flooding & degradation • Intensified storms / Extreme weather (droughts, floods, tropical storms, etc.) • Spread of water borne & tropical diseases

  25. 5 Scariest Things About Climate Change!!! http://www.youtube.com/watch?v=M2Jxs7lR8ZI

  26. Essential Question #4 What factors affect Earth’s average temperature?

  27. Factors Affecting Climate Change • Positive Feedback Mechanisms • Factors that amplify climate changes • Negative Feedback Mechanisms • Factors that dampen / reduce climate changes

  28. Oceans • Store CO2 & heat in deep (-) • How much can it handle? Unknown • Increased temperatures cause increased release of dissolved CO2 (+) • Increased evaporation can add H2O vapor, increasing warming (+) • Currents pull warm water north • Ice melt could disrupt currents • Disrupted currents could lead to cooling of N. Hemisphere

  29. Clouds • Warmer temp’s create more clouds • Could warm by trapping heat (+) or cool by reflecting sunlight (-) • Jet Contrails may have an impact • Can form high thin clouds, trapping heat (+)

  30. Pollution • Aerosols (microscopic droplets or particles) & soot can warm of cool air depending on size and reflectivity • Sulfate particles tend to cool (-) • Soot tends to warm (+) • Not likely to have a major impact, b/c don’t remain in atmosphere long & emissions being reduced

  31. Photosynthesis & Methane • Higher CO2 levels would increase photosynthesis which would remove CO2. (-) • Temporary - CO2 released when plants decay or burn & mature plants remove less CO2 • CH4 (methane) released from bogs, wetlands, deep ocean floor & tundra soil (permafrost) faster in warmer temps (+) • https://www.youtube.com/watch?v=NVpQnpWS2wU

  32. Essential Question #5 What are some possible beneficial and harmful effects of a warmer earth?

  33. Winners & Losers • Some areas will benefit from climate change, while others will lose. • Depends mostly on where you live • Poor nations in the tropics will suffer most

  34. EFFECTS OF GLOBAL WARMING • Between 1979 and 2005, average Arctic sea ice dropped 20% (as shown in blue hues above). Figure 20-8

  35. Sea Ice Melt: Pros & Cons CONS • As planet warms, convection transfers surplus heat to poles, increasing melting • More water exposed b/c of melt causes increase heat absorption PROS • Opens new areas to shipping and oil/gas exploration • Increase some commercial fisheries

  36. Land Ice / Mountaintop Glacier Melt: Pros & Cons CONS • Increases sea levels • Rivers & streams fed by glacial melt running dry • Fresh water shortages • Releases stored CO2 & CH4 PROS • Increased agriculture & timber harvest in some areas • Longer growing seasons • Increased tourism

  37. Rising Sea Levels • During this century rising seas levels are projected to flood low-lying urban areas, coastal estuaries, wetlands, coral reefs, and barrier islands and beaches. Figure 20-10

  38. Rising Sea Levels • A 2008 U.S. Geological Survey report estimates a sea level rise of 3.0 - 6.5 ft (0.8-2 m) by 2100, with rise continuing for centuries Figure 20-9

  39. Rising Sea Levels • If seas levels rise by 4-35 in (9-88cm) during this century, most of the Maldives islands and their coral reefs will be flooded. Figure 20-11

  40. Thermohaline Circulation:Changing Ocean Currents • Global warming could alter ocean currents and cause both excessive warming and severe cooling. Figure 20-12

  41. Weather Extremes Shifting patterns of precipitation will increase / intensify droughts in some areas, while other areas will be affected by severe flooding from prolonged / excess precipitation. Researchers have not been able to show that hurricane / typhoon activity will increase, but an MIT study indicates that size and strength can increase b/c of warmer surface waters

  42. Biodiversity • Could expand ranges & populations of species that could adapt to warmer climate • At least 1 million species could face premature extinction (especially specialized species or those w/ narrow ranges of tolerance) • Most threatened ecosystems: • coral reefs, polar seas, coastal wetlands, alpine/arctic tundra, & mountain-tops

  43. Agriculture & Human Health • In a warmer world, agricultural productivity may increase in some areas and decrease in others. • Crop and fish production in some areas could be reduced by rising sea levels that would flood river deltas. • Global warming will increase deaths from: • Heat and disruption of food supply. • Spread of tropical diseases to temperate regions. • Increase the number of environmental refugees.

  44. Agriculture Water Resources Forests • Changes in forest composition and locations • Disappearance of some forests, especially ones at high elevations • Increased fires from drying • Loss of wildlife habitat and species • Changes in water supply • Decreased water quality • Increased drought • Increased flooding • Snowpack reduction • Melting of mountaintop glaciers • Shifts in food-growing areas • Changes in crop yields • Increased irrigation demands • Increased pests, crop diseases, and weeds in warmer areas Biodiversity Sea Level and Coastal Areas • Rising sea levels • Flooding of low-lying islands and coastal cities • Flooding of coastal estuaries, wetlands, and coral reefs • Beach erosion • Disruption of coastal fisheries • Contamination of coastal aquifiers with salt water • Extinction of some plant and animal species • Loss of habitats • Disruption of aquatic life Weather Extremes Human Health • Decreased deaths from cold weather • Increased deaths from heat and disease • Disruption of food and water supplies • Spread of tropical diseases to temperate areas • Increased respiratory disease and pollen allergies • Increased water pollution from coastal flooding • Increased formation of photochemical smog Human Population • Prolonged heat waves and droughts • Increased flooding from more frequent, intense, and heavy rainfall in some areas • Increased deaths from heat and disruption of food supplies • More environmental refugees • Increased migration Benefits and Negative Impacts of Global Warming

  45. Essential Question #6 Why is global warming a difficult problem?

  46. Why is this such a difficult problem? • Many complex causes • Global problem • Long term issue • Harmful & beneficial impacts not spread equally • We can’t stop it, but we can slow it down • Some actions disrupt economies & lifestyles • Solutions: • Will require International Cooperation • Must be long-term, not within the scope of our lifetimes

  47. Strategies • Mitigation • Reduce greenhouse gas emissions to slow rate of temperature increase • Adaptation • Recognize that some warming is unavoidable & devise strategies to reduce its harmful effects

  48. When should we act? • Wait & See – U.S. • Act Now & Reduce Risk – Europe • + 2500 scientists & 2700 economists • Act Now as No Regrets Strategy • Even if problems don’t arise, still improving health of planet

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