7 th Grade Science. Unit: Global Warming Mini Unit Lesson: GW 2_Global Warming. Class Objectives: Students will be able to..

Transcription

1 7 th Grade Science Unit: Global Warming Mini Unit Lesson: GW 2_Global Warming Name: Date: Wednesday, October 12, 2016 Homeroom: Class Objectives: Students will be able to.. SWBAT describe the causes of global warming by explaining the effects of increased greenhouse gases. Do Now 1. What is your definition of global warming? 2. In the media, the phrases global warming and climate change are often used. Do you think these phrases mean the same thing? Why or why not? 3. How does the Earth stay warm? 1

2 Class Notes Causes of Global Climate Change Increase in,, and Increase in the (Earth s natural heating process and gases in atmosphere trap heat) CO2 Gases are used by during. Everybody Writes Explain why planting more trees and grass could help minimize global warming. 2

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4 Guided Practice Greenhouse Effect The warming of Earth's surface and lower atmosphere tends to intensify with an increase in atmospheric carbon dioxide. The atmosphere allows a large percentage of the visible light rays from the Sun to reach Earth's surface. Some of this energy is reradiated by Earth's surface in the form of long-wave infrared radiation. Much of this infrared radiation warms the atmosphere when it is absorbed by molecules of carbon dioxide and water vapor. A similar warming effect is produced by the glass of a greenhouse, which allows sunlight in the visible range to enter, but prevents infrared radiation from leaving the greenhouse. The absorption of infrared radiation causes Earth's surface and the lowest layer of Earth's atmosphere to warm to a higher temperature than would otherwise be the case. Without this "greenhouse" warming, Earth's average surface temperature could be as low as -73 C. The oceans would freeze under such conditions. Many scientists believe that modern industrialization and the burning of fossil fuels (coal, oil, and natural gas) have increased the amount of atmospheric carbon dioxide. This increase may result in an intensified greenhouse effect on Earth causing significant alterations in climate patterns in the future. Scientists estimate that average global temperatures could increase by as much as 5 C by the middle of the 21st century. 4

5 5. What causes Earth s surface to warm to a higher temperature? 6. How would the Earth be different if there weren t any greenhouse gases in the atmosphere? 7. How have humans contributed to the increase of atmospheric carbon dioxide? 8. State one possible change humans could make to significantly reduce the amount of greenhouse gases added to the atmosphere each year. 9. Describe the cartoon shown at right. What was the artist trying to suggest? 5

6 10. Summarize: What is causing the change in global climate? Who is most responsible for this and why? 11. Earth s very early atmosphere consisted mostly of carbon dioxide. When plants evolved, plants turned carbon dioxide into oxygen. Deforestation is the cutting down and clearing away of trees from forests. How does deforestation contribute to global warming? 12. Explain how the effect of global warming on present-day continental glaciers could affect New York City and Long Island. 6

7 Independent Practice August Cow Farts: Global Warmers Or A Load Of Hot Air? Scientists and farmers around the world are debating a very serious subject at the moment. Cow farts. Yes, really, they're talking about farting cows. They're talking about cow burps as well, and sheep burps, and even sheep farts. Why? Good question. Let's start with a look at the science behind wind. Farts and burps are basically pockets of gas that get released from human and animal bodies. Some gas is swallowed, like oxygen, when we eat or talk. Some of it is created inside our bodies as we digest food. This gassy mixture isn't useful, so our bodies push it out and away as best they can... in burps and farts. Got it so far? Hope you're not giggling by the way, this is very serious science One of the gases found in farts and burps is called 'methane'. A certain amount of methane in the atmosphere is natural, and is a good thing. Along with other so-called 'greenhouse gases' methane collects in the sky and traps warm air around our planet. Problems begin when the layer of greenhouse gases gets too thick and traps too much heat. This is called 'global warming'. It's now a proven fact that our planet is warming up very quickly. And, most scientists agree that this is because of greenhouse gases, including methane. Which takes us back to our farting farm animals. A scientific report published in California last week claimed that dairy cows in the area were producing almost 20 pounds (in weight, that's almost 10 kg) of gas every year, each. That's a huge, huge amount. If that figure is accurate, it could mean that cow farts were causing more global warming than pollution from cars in that region, as millions of cows live there. Trouble is, the local farmers don't believe the report. They reckon their cows are far less windy than that and are questioning the way the research was done. Scientists around the world have known for years that animal wind could be a problem. What they can't agree on is how much of a problem. It's very difficult to measure just how much methane an animal is burping and farting out. Even if scientists manage to measure the size of the farts or burps, they then have to work out how much methane they contain. Another problem is that methane doesn't 7

8 only come from windy animals. It's released when trash is processed for instance... which means more measuring and more 8

9 1. Why do scientists believe cows contribute to global warming? 2. Why is it difficult to measure how much cows are contributing to global warming? Average temperatures on Earth are primarily the result of the total amount of insolation absorbed by Earth s surface and atmosphere compared to the amount of long-wave energy radiated back into space. Scientists believe that the addition of greenhouse gases into Earth s atmosphere gradually increases global temperatures. 1. Identify two major greenhouse gases that contribute to global warming. and 2. Explain how increasing the amount of greenhouse gases in Earth s atmosphere increases global temperatures. 9