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  1. 7.1 7.1 Factors that Affect Climate Change

  2. 7.1 Views on Climate Change “A variety of views are held on the issue of climate change, the seriousness of the problem, the human contribution to the problem, and the actions that must be taken” What are your views on this issue? Activity 7-1 on page 267

  3. 7.1 Factors that Affect Climate Change • Atmosphere: A layer of gases that surrounds a planet or moon • Weather: Condition of the atmosphere in a specific place at a specific time (describes wind, temp, moisture) • Climate: Characteristic weather patterns within a region averaged over a long period of time (Temp, wind velocity)

  4. 7.1 Factors that Affect Climate Change • Earth has experienced many climate changes in the past

  5. 7.1 Earth and Sun • Sun’s energy is the most important factor affecting climate on Earth (winds, rain etc) • The amount of radiation produced by the sun varies and a regular solar cycle (sunspot cycle) occurs every 11 years • When the number of sunspots is high, the Sun emits higher amounts of solar radiation.

  6. 7.1 Earth and Sun • Earth rotates tilted (23.5º) on an axis every 24 hrs • the combination of Earth’s annual orbit and its tilted axis produces the seasons

  7. 7.1 Earth and Sun

  8. 7.1 Earth and Sun

  9. 7.1 Changes in Earth’s Orbit • Earth’s orbit, tilt and rotation change in repeating cycles • Milankovic (mathematician) found these variations change the amount of solar energy hitting the Earth • (1) Eccentricity: every 100 000 years, Earth’s orbit changes from circular to elliptical • Elliptical orbit means more solar energy for Earth which affects length of seasons

  10. 7.1 Changes in Earth’s Orbit • (2) Tilt: Earth’s tilt changes every 41000 years by about 2.4º • The greater the tilt, the greater the temperature differences between summer and winter • (3) Wobble: Earth wobbles (precesses) since it is not a perfect sphere • This wobble affects the amount of solar energy hitting the northern and southern hemispheres

  11. 7.1 Effect of Latitude on Climate & Seasons • The equator is hotter since the sun’s rays strike the Earth at 90 • A ray hitting the Earth at 45 south strikes the Earth at an angle spreading the energy over an area 1.5 times larger • At the poles, rays are spread out even more; each square meter of area receives even less energy Do Questions # 1-4 on page 272

  12. 7.1 How Atmosphere Affects Climate • Atmosphere is made of N2, O2 and H2O; absorbs energy from Sun and traps energy from Earth’s surface • Greenhouse Effect: Warming caused when the atmosphere absorbs thermal energy radiated by the Sun and Earth

  13. 7.1 Winds Disperse Energy in Atmosphere • Wind: The movement of air from an area of high to low pressure as a result of uneven heating • Transfers thermal energy around the world from warm to cooler areas; affects ocean currents and precipitation patterns

  14. 7.1 Winds Disperse Energy in Atmosphere

  15. 7.1 Winds Move Ocean Currents • Ocean currents are driven by the wind • Energy from the moving air is transferred to the surface of the water – causing water to move • Oceans absorb energy from the sun; movement of water transfers heat around the Earth’s surface • Prevailing winds: wind that blows in a constant direction around the world

  16. 7.1 Winds Disperse Energy in Atmosphere

  17. 7.1 Winds Affect Precipitation • As one air mass rises above another, the rising air cools and water vapor condenses forming precipitation • Jet Streams: high-altitude winds that travel long distances at high speeds – carry warm moist air producing precipitation or dry air causing dry weather

  18. 7.1 Winds Affect Precipitation • Photograph taken from space shuttle 320 Km above the Earth; shows a band of cirrus clouds produced by a westerly jet stream that stretches across the Red Sea from Sudan to Saudi Arabia.

  19. 7.1 How the Hydrosphere Affects Climate • Hydrosphere: Collective mass of water on Earth in liquid, solid and vapor form • Oceans & lakes are a heat reservoirs; buffer temperature changes in the atmosphere (water has a high specific heat capacity) • Specific Heat Capacity: The amount of heat required to raise the temperature of 1g of substance by 1ºC • Ocean temperatures change very slowly

  20. 7.1 How the Hydrosphere Affects Climate • Earth’s Albedo: the fraction of light that is reflected by the surface of Earth back into space • Snow and ice reflect solar radiation (because of their color) • The ocean reflects 7% of solar energy; fresh snow can reflect up to 90% - these differences affect average global temperature

  21. 7.1 How Moving Continents Affect Climate • Tectonic Plate: Piece of the Earth’s shell that moves around on flowing underlying rock • Earth has 12 major plates; changing distribution of land and water affects air patterns, water circulation and transfer of thermal energy • Volcanic eruptions spew particles in the air which reflect solar radiation and have a cooling effect

  22. 7.1 How Human Activity Affects Climate • Anthropogenic: Relating to or resulting from the influence of humans • Human technologies affect the atmosphere; burning coal, oil and natural gas • Since the industrial revolution in the 1700’s, the amount of greenhouse gases released into the atmosphere has increased

  23. Do Questions # 1-8 on page 278