1. Unit 4: Climate Change Earth’s Climate System

2. Introduction Atmosphere: layer of gases that surrounds a planet or moon Without the atmosphere, days would be scorching hot and nights freezing cold

3. Introduction Conditions within the atmosphere at a specific place and time = weather

4. Introduction Climate: the characteristic pattern of weather conditions within a region -Includes: temperature, wind velocity, precipitation, and other features -Averaged over a long period of time

5. The world is divided into 5 major climate zones based on: - average monthly temperature and precipitation - average annual precipitation Climate ZoneDescription 1. Tropical moist climate All months average above 18 ∘ C Annual precipitation greater than 1500 mm 2.Dry climateTemp range from 40 ∘ C to - 40 ∘ C Low precipitation, exceeded by evaporation 3. Moist, mid- latitude climate with mild winters Warm to hot summers No colder than -3 ∘ C on average in cold months 4. Moist, mid- latitude climate with cold winters Warm to cool summers Average below -3 ∘ C in colder months 5. Polar climateCool summers and extremely cold winters Where does Ottawa fit in?

6. Factors that affect climate change Climates around the world have changed many times over the billions of years of Earth’s history Many natural factors affect climate change.

7. 1. The Sun The single most important factor that affects climate on Earth Energy travels to Earth in form of light and heat Affects temperature, precipitation and wind Four factors: a. Changes in solar activity b. Movements of Earth in Space c. Changes in Earth’s rotation, orbit and tilt d. Latitude

8. 1a. Solar Activity Amount of solar radiation varies with irregular fluctuations There is also a regular solar cycle (sunspot cycle) Variations in solar output historically have been attributed to be the main cause of climate change

9. 1b. Movements of Earth in Space Earth rotates on its axis every 24 hours Earth orbits around the Sun every 365 days Earth is tilted at an angle of 23.5 All of these factors produce the seasons.

10. 1c. Rotation, Orbit and Tilt Eccentricity: due to gravitational attraction of other planets, Earth’s orbit fluctuates slightly from circular to elliptical (cycle of 100000 years) Tilt: angle of tilt varies by 2.4 every 41 000 years - greater the angle = greater the difference between winter & summer A. circular orbit B. elliptical orbit

11. 1c. Rotation, Orbit and Tilt Wobble: Earth is not a perfect sphere, so it wobbles slightly as it rotates on its axis. – affects amount and intensity of solar energy received at different parts of the year

12. 1d. Latitude Sun’s rays strike the Earth at different angles due to its curved shape

13. 1d. Latitude At the equator, rays strike directly perpendicular to surface At latitude of 45 south, rays strike at an angle, so energy is spread out over a greater distance

14. 2. The Atmosphere and Wind The atmosphere extends up from surface to 560 km into space Composed mainly of nitrogen gas, oxygen gas and water vapour Absorbs thermal energy from the Sun and from Earth’s surface  Greenhouse effect Helps to keep temperature variations within a certain range

15. Role of Wind Wind: movement of air from area of high pressure to area of low pressure i) Winds disperse energy through atmosphere -Wind transfers thermal energy from warm to cool areas (high to low pressure)

16. Role of Wind Wind: movement of air from area of high pressure to area of low pressure i) Winds disperse energy through atmosphere -Wind transfers thermal energy from warm to cool areas (high to low pressure)

17. Role of Wind ii) Winds move ocean currents -As winds move across the surface of water, energy is transferred to the water, causing water to move -Water absorbs energy from the Sun -Movement of water results in transfer of heat around Earth’s surface Prevailing global wind patterns and ocean currents

18. Role of Wind ii) Winds move ocean currents

19. iii) Winds affect precipitation -As air masses move across Earth’s surface, they interact -One mass (the lighter one) usually rises above the other -Rising air cools and water vapour in the air condenses to form precipitation

20. iii) Winds affect precipitation - Jet streams: high altitude winds that travel at high speed may carry warm, moist air (causes precipitation) or dry, cool air (causes dry weather)

21. iii) Winds affect precipitation - Jet streams: high altitude winds that travel at high speed may carry warm, moist air (causes precipitation) or dry, cool air (causes dry weather) Jet stream (as seen from space)

22. 3. The Hydrosphere Hydrosphere: all water found on, under and over the surface of Earth in the form of liquid water, ice or vapour Oceans hold much more heat than the atmosphere – act as a heat reservoir A lot of energy is required to change the temperature of water by even one degree Celsius  temperature of large bodies of water changes slowly and by small amounts

23. Ice and snow reflect solar radiation because of their light colour Albedo: the fraction of energy reflected by a surface (largely determined by colour) A large surface of snow or ice will reflect up to 80 or 90% of the solar energy that strikes it In comparison, the ocean surface reflects only 7% The distribution of water, ice & land greatly affects temperature 3. The Hydrosphere

24. 4. The Moving Continents Earth’s outer layer is composed of massive pieces of rock called tectonic plates The plates move at a rate of a few cm each year, carrying continents with them Shape of oceans and continents is always changing slightly, affecting patterns of heat transfer through air and water

25. Volcanoes are located at boundaries of tectonic plates  when volcanoes erupt, ash and other particles are spewed into the atmosphere Particles reflect solar radiation and cool the climate Effect may last a few years to several decades 4. The Moving Continents

26. Anthropogenic Factors Some scientists believe that natural factors alone can’t account for the rate of climate warming seen since 1970 Some studies suggest that recent climate change is at least partly anthropogenic (caused by human activity)

27. The Industrial Revolution (starting in the late 1700s) saw a rapid increase in rate at which new machines were invented  Required fossil fuels to power them Technologies that burn fossil fuels grew and spread Burning fossil fuels releases energy, but also gases and pollutants that affect the natural processes that control the greenhouse effect Anthropogenic Factors

28. p. 278 #1 – 8 Crossword Homework