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Global Warming

Global Warming. What is global warming? Is it real? What is causing global warming?. Global warming in the news/popular culture. Global warming is when the Earth’s overall temperature rises. t ake a thermometer outside and measure the temperature every day at the same location for a year

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Global Warming

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  1. Global Warming What is global warming? Is it real? What is causing global warming?

  2. Global warming in the news/popular culture

  3. Global warming is when the Earth’s overall temperature rises • take a thermometer outside and measure the temperature every day at the same locationfor a year • average these temperatures together and you have the average yearly temperature of the location • do the same for many locations on the earth and average those together – this is the average temperature of the Earth for that year! • repeat for many years and plot the results…is the temperature rising?

  4. So

  5. Tricks people may play with statistical data… • showing you temperature data for only one location • showing you data that has been improperly “processed” (e.g. early satellite data) • showing you irrelevant and misinterpreted data (e.g. data for higher atmospheric levels) • stretching or shrinking axes Be careful with what you believe!

  6. By stretching and shrinking various axes, I can make the amount of warming look more (left) or less (bottom) dramatic!

  7. What can cause the earth to warm up? • Variations in solar intensity • Variations in the Earth’s orbital properties (for example eccentricity) • Variations in the amount of greenhouse gases in the Earth’s atmosphere

  8. What is light? • Light is an electromagneticwave • There are varying wavelengths and frequencies

  9. The electromagnetic spectrum

  10. Important point • All objects (solid, liquid, or gas) absorb and emit em radiation! • They can absorb and emit different wavelengths

  11. The greenhouse effect Outgoing long wavelength energy escapes to space Incoming solar energy (mostly visible light) Incoming solar energy is absorbed by the surface and re-emitted at longer wavelengths (mostly infrared light)

  12. The greenhouse effect Incoming solar energy Outgoing long wavelength energy is trapped by the greenhouse Incoming solar energy is absorbed by the surface and re-emitted at longer wavelengths

  13. The greenhouse effect Incoming solar energy Outgoing long wavelength energy is trapped by greenhouse gases Incoming solar energy is absorbed by the surface and re-emitted at longer wavelengths Note: the size of the greenhouse gas molecules is exaggerated!

  14. Common greenhouse gases • water vapor (H2O) • carbon dioxide (CO2) • methane (CH4) • nitrous oxide (N2O) Question: Which greenhouse gas contributes the most to warming the Earth?

  15. The Earth’s average temperature is about 60 degrees Fahrenheit…what would it be if there wasn’t a greenhouse effect? • about 60 degrees Fahrenheit (the same) • about 90 degrees Fahrenheit • about 20 degrees Fahrenheit • about 0 degrees Fahrenheit

  16. Venus is our nearest neighbor. Yet it is the hottest planet. Why? It is 820 degrees Fahrenheit during a typical day on Venus! Recall that: -water boils at 212 degrees F -lead, zinc, and tin all melt below this temperature

  17. Practice • In groups, complete the “The Greenhouse Effect” worksheet (handed out).

  18. Question Which statement most accurately describes the greenhouse effect? • Greenhouses gases trap incoming visible light before it hits the surface. • Greenhouse gases increase the surface’s ability to absorb visible light. • Greenhouse gases trap outgoing infrared light. • Greenhouse gases allow ultraviolet light to pass through to the surface. • All of the above contribute equally.

  19. Practice • In groups, complete the lecture tutorial entitled “Climate Change and Carbon Dioxide,” which begins on page 65 of your tutorial book.

  20. Question What is the relationship between the amount of carbon dioxide in the atmosphere and the average surface temperature of the Earth? • There is no relationship. • The more carbon dioxide, the warmer the temperature. • The more carbon dioxide, the colder the temperature.

  21. Questions True/False: “The amount of carbon dioxide in the Earth’s atmosphere is currently greater than it has been at any time in the past 400,000 years.” True/False: “The average temperature of the Earth’s surface is currently greater than it has been at any time in the past 400,000 years.” True/False: “Within the next 100 years, there will be so much carbon dioxide in the atmosphere that humans will have trouble breathing.” True False: “Within the next 100 years, the Earth’s temperature will become too hot for humans to survive.

  22. But how do we know how much carbon dioxide was in the atmosphere in the year 500?? • ice cores from Antarctica, Greenland, or mountain glaciers

  23. So…. • We know the Earth is warming. • We know that the amount of greenhouse gases in the atmosphere is increasing due to human activity. Does this mean that humans are causing the warming??

  24. Global climate models (GCM’s)

  25. The IPCC – Intergovernmental Panel on Climate Change • established by the United Nations to evaluate whether there is a problem and to make recommendations • 4 major reports so far, from the last: • Most of the observed increase in globally averaged temperatures since the mid-20th century is very likelydue to the observed increase in anthropogenic greenhouse gas concentrations.

  26. Also… Over 95% of scientists who work in climate change agree that humans are causing warming

  27. Magnitude of warming • Look back at the warming graph…how much has the near surface temperature of the Earth increased over the last century?  0.74 degrees Celsius (1.33 degrees Fahrenheit)  over the next 100 years, 2-5 more degrees Celsius (3-9 degrees Fahrenheit) • Do you think this is a lot? • What are the possible effects of global warming?

  28. When carbon dioxide doubles (~100 years from now) Winter Summer

  29. Questions you should be able to answer. • What is global warming? • Has the Earth’s temperature increased over the past century? Is so, by about how much? • What processes can cause the Earth to warm up? • Describe the greenhouse effect – how does it work? • What are some common greenhouse gases? • Has the amount of carbon dioxide in the atmosphere increased over the past few centuries? If so, from what? • What do scientists think is causing global warming? • How do they know?

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