Climate Change Lecture Notes

Transcription

1 Climate Change Lecture Notes (Topic 12A) page 1 Climate Change Lecture Notes Learning Outcomes for the Climate Change Unit 1. Students can list observations which suggest that the world is warming, and explain how or why the evidence indicates that the world is warming. 2. Students can describe how visible and infrared electromagnetic waves interact with the atmosphere and the surface of the Earth, and explain how this warms the planet (i.e., explain the greenhouse effect). 3. Students can identify the major ways in which human actions are affecting the average temperature of the Earth, and how and why they affect the temperature of the Earth. 4. Students can describe how the ocean redistributes heat between the Equator and the Poles. 5. Students can identify the major ways in which the ocean affects the average temperature of the Earth, and explain how and why the ocean affects the average temperature of the Earth. 6. Students can describe and explain how and why the amount of clouds in the atmosphere affects the average temperature of the Earth. 7. Students can describe the major ways in which the warming of the Earth s oceans and the increased levels of carbon dioxide in the ocean will affect ocean life and humans, and explain why the changes in the temperature and chemical composition of ocean water will have these impacts. 8. Students can describe the thermohaline circulation (THC) and what causes the THC, and explain how and why the THC affects the overall temperature of the Earth and the climate at the Poles. 9. Students can describe how ocean life permanently removes carbon dioxide from the ocean and atmosphere, and discuss how changes to the ocean environment would affect the rate at which life removes carbon dioxide and the implications for the overall temperature of the Earth.

2 Climate Change Lecture Notes (Topic 12A) page 2 Climate vs. Weather In this class we focus on climate, not weather. Climate is the long-term average of weather conditions (what the weather is usually like). For example, Southern California has a warm, dry climate. This does not mean that it is always warm (we have our cooler days) or that it does not rain in Southern California; it means that our weather is warm most of the time and that rain is less common here than elsewhere. Another way to think about it: weather is what conditions are like a particular day, climate is what conditions are typically like over a season or a year. Which of the following are examples of climate? Which are example of weather? During January through March of 2013, California received only 26% of normal amount of rain that in usually gets during these months. The highest temperature recorded in Los Angeles County was 80 o F yesterday. In March of 2012, nearly 80% of places where temperature measurements are regularly recorded in the United States were much warmer than normal (far above average) for March. This afternoon there is less than a 10% chance of rain.

3 Climate Change Lecture Notes (Topic 12A) page 3 Electromagnetic Waves ( EM waves ) Electromagnetic waves are disturbances (ripples, wiggles) in the electromagentic fields surrounding electrically-charged particles like electrons and protons. Electromagnetic waves are named for the size of the disturbance ( wiggle ). Fast-wiggling, small disturbances are called high frequency, short-wavelength EM waves, and slow-wiggling, large disturbances are called low frequency, long-wavelength EM waves. The collection of all of the different kinds of electromagnetic waves is called the electromagnetic spectrum. 273 K Examine the chart above. Notice the arrow pointing the wavelength row. Give examples of short-wavelength EM waves: Give examples of long-wavelength EM waves: Each kind of atom and molecule emits ( sends away ), reflects, and absorbs certain specific kinds of electromagnetic waves, because each kind of atom and molecule has its own unique number and arrangement of electrons and protons. If an atom or molecule cannot emit, reflect, or absorb a certain kind of electromagnetic wave, then these waves go through these atoms and molecules! In other words, these atoms and molecules are transparent to this kind of electromagentic wave. Think about your own observations and experiences as you answer the next 3 questions: Visible light cannot go through most substances. What substance(s) can visible light go through? What substances can X-rays go through? What substances absorb and thus block X-rays? Courtesy of NASA

4 Climate Change Lecture Notes (Topic 12A) page 4 You cannot see all kinds of electromagnetic waves (EM waves) because the rods and cones in your eyes are tuned so that they only send a signal to your brain when they pick up certain specific kinds of EM waves: visible light (red, orange, yellow, green, blue, violet). Even if you cannot see EM waves, they can still affect you: the atoms and molecules of your body can absorb them. Electromagnetic waves are created when electric objects like atoms and molecules move (e.g., wiggle). Since the atoms and molecules of objects are always moving, objects are constantly emitting (sending away) energy in the form of EM waves. Of course, the warmer an object is, the more energy it can and does emit. A temperature of 273 K is about 0 o C, the freezing point of water. Refer to the chart on the previous page. What kind of light does an object emit if it has a temperature of 0 o C? When it is dark, you cannot see most objects because there is no visible light reflecting off them and into your eyes. If an object emits visible light, on the other hand, you can see it in the dark because it creates visible light. Consider your own experience: Does room-temperature wood emit visible light? Does burning wood emit visible light? Wood typically burns at a temperture of about 232 o C. Based on this information and your answers to the questions above, why don t most ordinary objects (like those in the room around you right now) emit visible light? How could you get the objects in the room around you to emit visible light? What kind of EM waves do most objects in the room around you right now emit? If an object absorbs EM waves, the object will get (A). If an object emits (sends away) EM waves, the object will get (A). Hot objects emit (B) EM waves ( heat ) than cold objects. Very hot objects can emit (C) EM waves, but objects at room temperature or colder emit (C) EM waves. Very cold objects (D) emit EM waves ( heat ). A: warmer, colder B: more, fewer C: visible light, infrared D: do, do not

5 Climate Change Lecture Notes (Topic 12A) page 5 Greenhouses What is a greenhouse? Why is it called a green house? What happens to visible light when it hits glass? What happens to infrared light when it hits glass? Windshield Car Seat What happens to the heat emitted as infrared light by the car seat? Where is the car seat receiving heat from? In other words, what kinds of EM waves are hitting it and what are emitting them? The car seat is warmer because it is surrounded by windows. Why would the car seat be cooler if there were no windows?

6 ACTIVITY: Greenhouse Gases and the Greenhouse Effect Greenhouse gases only absorb infrared light; other kinds of light pass through them. Explain how the greenhouse effect works by filling in the spaces below. The Sun emits mainly (A) light which (B) the nitrogen and oxygen in the atmosphere and (B) Climate Change Lecture Notes (Topic 12A) page 6 the greenhouse gases in the atmosphere like. The sunlight (B) the surface of the Earth, making the surface of the Earth warmer, both the land and the ocean. The warmer they get, the more heat the land and ocean send away as (A) light. This light (B) the nitrogen and oxygen in the atmosphere but (B) the greenhouse gases in the atmosphere, making the greenhouse gases warmer and thus warming the atmosphere. The warmer the atmosphere gets, the more heat the atmosphere sends away as (A) light. About half is sent out into space, and about half is sent back to the surface of the Earth, making the Earth warmer. Possible Answers A: x-rays, ultraviolet, visible, infrared B: goes through, is absorbed by, is reflected by The Earth is warmer because it is surrounded by greenhouse gases. Why would the Earth be cooler if there were no greenhouse gases in the atomsphere? If there were no greenhouse gases in the atmosphere, what would the Earth be like? visible Atmosphere CHECK YOUR ANSWERS WITH YOUR INSTRUCTOR

7 Climate Change Lecture Notes (Topic 12A) page 7 Global Warming Aside from direct temperature measurements, what other observational evidence is there that the world has been and is getting warmer? How or why do these observations suggest that the world is getting warmer? In each case, explain your reasoning. Glaciers and Ice at the Poles Sea Level Animal Behavior What is currently the best idea that explains why the world has warmed over the last 100 years or so? In other words, what idea is best supported by the observational evidence that we currently have? What alternative ideas are well-supported by the evidence? If an idea is well-supported by the evidence, do scientists call the idea a hypothesis or a theory? Where does a large amount of our carbon dioxide pollution go each year?

8 The Earth s Climate: Important Influences Sunlight Climate Change Lecture Notes (Topic 12A) page 8 The amount of sunlight and where it falls changes due to variations in the Earth s orbit and tilt ( Milankovitch cycles ). Plate Tectonics Creates Volcanoes Changes Wind & Rainfall Patterns: Mountains rise and block winds. Land and ocean have different temperatures due to their different heat capacities so as continents move, winds shift and blow in different directions. Changes in Ocean Circulation (including the thermohaline circulation) Changes in amount of sunlight reflected and absorbed: The Ocean continents move: in some positions, ice and snow can build up See the Climate Change Homework for detailed examples.

9 Climate Change Lecture Notes (Topic 12A) page 9 The Atmosphere Greenhouse Gases Clouds Cloud Cloud Dust The ocean affects the amount of greenhouse gases, clouds, and dust in the atmosphere. How does the ocean affect the amount of each one? Greenhouse Gases Clouds Dust

10 Climate Change Lecture Notes (Topic 12A) page 10 Past Changes in Climate Earth s Climate has been unusually stable for the last 10,000 years. Changes in temperature have been small (1-2 o C, 2-4 o F), but the small variations during the Medieval Warm Period and the Little Ice Age had significant effects. Give an example of a well-known, small change in climate due to changes in the ocean that has a significant impact on California s economy. Natural, large climate changes can happen quickly (over decades) because of changes in winds and ocean currents. Why did the thermohaline circulation shut down about 16,000 years ago? Ice Sheets 16,000 years ago Mississippi River Ice Sheets 12,500 years ago Did the shutdown of the THC circulation warm or cool Europe? Why? Explain your reasoning. St Lawrence River Why did the thermohaline circulation eventually start again? Equator North Pole Did the thermohaline circulation starting again warm or cool Europe? Why? Explain your reasoning.

11 Is Global Warming Bad? Why or Why not? People who live near the Poles Climate Change Lecture Notes (Topic 12A) page 11 People who live near the Equator People who live near the Coast Shipping & Mining Resources in the Arctic Will it really be Global Warming? If the Earth s climate continues to warm, the ice sheets on Greenland will melt, and the thermohaline circulation could shut down. Why? Greenland Ice Sheet Will this cause Europe to get warmer or colder? Why? Explain your reasoning.

12 Climate Change Lecture Notes (Topic 12A) page 12 Climate Change Review Quiz 1. What kind of light do not-very-hot objects emit? a. X-rays b. Ultraviolet c. Visible d. Infrared 2. Greenhouse gases like carbon dioxide absorb visible light. a. True b. False 3. Does the thermohaline circulation warm or cool the world overall? What is the primary way that the thermohaline circulation affects the overall climate of the Earth? a. Warms: warms the surface of the ocean b. Warms: increases the greenhouse effect c. Cools: cools the surface of the ocean d. Cools: reduces the greenhouse effect e. No Overall Effect: warm and cold water just switch places How or why does the motion of the water in the thermohaline circulation produce these effects? 4. Why does the water rising upwards in the thermohaline circulation have such low levels of carbon dioxide? a. the water is old : bacteria have had a long time to decompose the carbon dioxide in the water b. the water is old : the last time that the water was in contact with the atmosphere was a long time ago when there was less carbon dioxide in the atmosphere c. the water comes from deep in the ocean: sediments on the deep ocean floor absorb carbon dioxide from ocean water d. the water comes from deep in the ocean: special bacteria living in the deep ocean decompose the carbon dioxide

13 Climate Change Lecture Notes (Topic 12A) page The amount of carbon dioxide in the atmosphere has been going up for the last 50 years. This statement is: a. an observation that supports the theory that the world is getting warmer. b. an observation that supports the theory that a stronger greenhouse effect is causing the world to get warmer. c. a hypothesis with few or no observations supporting it. d. a theory with few or no observations supporting it. 6. Phytoplankton help clean up our pollution by absorbing carbon dioxide, and using it for a purpose which makes it less likely for the carbon dioxide to end up back in the ocean and/or atmosphere where it can cause harm. Which use makes it most likely that the carbon dioxide will be permanently removed from the environment and no longer able to cause harm? a. Breathing c. Dissolving e. Respiration b. Decomposing d. Photosynthesis f. Shells Where does the carbon go? Where is the carbon permanently stored?

14 7. How do clouds affect the Earth s climate? Climate Change Lecture Notes (Topic 12A) page 14 a. Warm the Earth c. Warm the Earth in some ways, and cool the Earth in other ways b. Cool the Earth d. Clouds do not have a significant impact on the temp. of the Earth Explain. 8. Aside from releasing greenhouse gases by burning fossil fuels and forests, how do humans have a major impact on the Earth s climate? a. Adding Dust ( Aerosols ) to the Air c. Filling in Wetlands b. Breathing d. Ocean Pollution Kills Phytoplankton