Chapter 13: Atmosphere and Climate Change

1. Chapter 13: Atmosphere and Climate Change

2. Discussion Prompt: What do you think about climate change? Share any thoughts that come to mind.

3. Section 13.1: Climate and Climate Change • Weather: state of the atmosphere at a particular place and time • Climate: long-term weather conditions at a particular place

4. What factors determine climate? • Latitude • Atmospheric circulation patterns • Oceanic circulation patterns • Local geography of an area • Solar activity • Volcanic activity

5. What factors determine climate? 1. Latitude: distance north or south from the equator. It determines the amount of solar energy that reaches an area of earth. • Low latitude – receive more solar energy, the energy is more concentrated, day and night equal in length temps high all year • High latitude – amount of solar energy is reduced and less concentrated, yearly average temps are low

7. 2. Atmospheric circulation • Cold air is more dense and sinks, as it sinks it is warmed • Warm air rises and can hold more water vapor, as air rises it cools and some water vapor may form rain, snow, or fog • Solar energy heats the ground and the ground heats the air • Wind: movement of air created when warm air rises and cool air moves in to replace it, circulation patterns are created by the rotation of the earth

8. 3. Global air circulation patterns – pg 353 • Prevailing winds: blow in predominantly one direction • Rotation of the earth deflects these winds to the right in the northern hemisphere and to the left in the southern hemisphere • Trade Winds – 0 to 30 degrees N and S • Prevailing Westerlies –30 to 60 deg N and S • Polar Easterlies – 60 to 90 deg N and S

10. 4. Oceanic Circulation patterns • Water holds a great deal of heat so ocean currents have a big effect on climate • Winds and the rotation of the earth cause the movement of surface ocean currents • El Nino – Southern Oscillation (ENSO) – periodic change in the location of warm and cold water masses in the Pacific • El Nino – (warm phase) winds in western pacific push warm water eastward, produces increased rainfall in Southern half of US and South America, drought in Indonesia and Australia • La Nina – (cold phase) water in eastern pacific is cooler than usual

12. 5. Topography - • height above sea level – temp decrease by 6 degrees Celsius for every 1,000 m rise • Mountain ranges – rain shadow effect • windward side – rainy, warm air rises and cools and created precip (western side) • leeward side – dry, cold air sinks and gets warmer (eastern side) , deserts often occur here

13. 6. Seasonal Changes in Climate • Cause for the seasons – tilt of the earth on it’s axis changes the angle at the which the sun’s rays hit the surface of the earth as it moves around the sun • Northern Hemisphere • Summer – tilted toward sun, longer and warmer days • Winter – tilted away from sun, shorter and cooler days • Opposite for Southern Hemisphere

14. Solar activity • Maunder Maximum: high solar activity=hotter • Maunder Minimum=low solar activity=colder

15. Volcanic Activity • Predict the relationship between volcanic eruptions and climate.

16. Section 13-2: The Ozone Shield • Discussion Prompt: • What do you think is the importance of the ozone layer? • Do you think it has been changing?

17. The Ozone Shield • Ozone layer: area in stratosphere where ozone is highly concentrated • Ozone: molecule of 3 oxygen atoms (O3) • Absorbs harmful UV light from the sun • CFC’s (chlorofluorocarbons): read p. 359 are chemicals that cause ozone depletion - -Broken apart in stratosphere by UV radiation, chlorine bonds with oxygen and keeps more ozone molecules from forming

19. The Ozone Hole Ozone Hole: A thinning of stratospheric ozone over the north and south poles • Based on data starting in 1979 from weather satellites and research in Antarctica • How does the hole form? • Formed within polar stratospheric clouds which convert CFC’s into chlorine molecules • in spring the UV rays split apart the chlorine molecules into single chlorine atoms which then destroy ozone

20. Ozone Hole, cont. • Effects of thinning ozone hole on humans- more harmful UV light reaches the earth’s surface • UV light mutates DNA, increases chance of skin cancer and other health issues • Effects on plants and animals – High levels of UV light can kill phytoplankton, disrupting ecosystems and increasing carbon dioxide (CO2) • Especially damaging to amphibians • Interferes with photosynthesis in plants • See Table 1 on p. 361

21. Protecting the Ozone Layer • 1987 Montreal Protocol • Nations agreed to limit production of CFC’s • 1992 – Denmark – nations agreed to elliminate most CFC’c by 1995 • US banned all substances harmful to ozone by 2000 • CFC’s remain in stratosphere for 60-120 years

23. Section 13-3: Global Warming • Discussion Prompt: Write everything you know or have heard about global warming.

24. Global Warming • Read the introduction on p. 363. • Greenhouse Effect: sunlight passes through the atmosphere as light energy and is absorbed by the earth, the earth radiates the heat energy out into the air and some of it is absorbed, warming the earth • Greenhouse gases: gases in the atmosphere that absorb heat from the earth • Water vapor, carbon dioxide, CFC’s, methane, oxides • Mostly water vapor and carbon dioxide

25. Carbon dioxide levels • Vary through the year • Summer: decreased levels due to plant activity (more photosynthesis) • Winter: increased due to dying plants (less photosynthesis) • Rising levels • Over 20% increase in the last 50 years • Due largely to emissions from burning fossil fuels • Earth’s Temperature – more greenhouse gases near surface will increase global temperatures

26. Global Warming • Global Warming: An increase in the average temperature at the earth’s surface • The rise in average temperature correlates with the rise in levels of greenhouse gases • Hypothesis – the rise in greenhouse gases has caused the rise in average temp • Well supported by thousands of experiments and computer models • Other possibilities – natural climatic variability • Modeling global warming – computer models use equations and current data to predict future changes • Models are not always completely accurate

27. Consequences of a warmer earth 1. Melting ice, rising sea levels – Polar landmasses are melting causing sea levels to rise • Could cause flooding of coastal wetlands and low-lying areas, beach erosion, altering of salinity levels in bays, estuaries and freshwater aquifers 2. Global weather patterns altered by warmer ocean waters • More hurricanes and typhoons • Change in ocean current patterns • Can alter total amount of rainfall received around the world 3. Human health problems increase -more heat related illnesses, longer allergy seasons, more diseases transmitted by insects like mosquitos

28. Consequences cont. 4. Agriculture effected by extreme weather events like droughts, could increase demand for water 5. Effects on plants and animals – • alter the range and composition of plant and animal communities • Shift in geographical range of animals • Some species could be eliminated due to warmer temps

29. Recent Findings • Intergovernmental Panel on Climate Chage (IPCC)- network of 2,500 of the worlds leading climatologists • TAR Third Assessment Report – describes current global climate and makes future estimates for the global climate • Findings: • Global temp up .6 °C during the 20th century • Snow cover and ice extent has decreased • Average global sea level has risen • Levels of atmospheric greenhouse gases continues to increase

30. Reducing the Risk • 1997 – 160 countries set timetables for reducing emissions of greenhouse gases • Kyoto Protocol – treaty that requires developed countries to decrease emissions of greenhouse gases by 5% of 1990 levels by 2012 • Has to be ratified by 55% of attending countries – US has not ratified it while most other countries have