- A
- B
- C
Listen to a lecture in a science class, take detailed notes while listening.
contend – to argue
cycle – a series of events that happen again and again throughout time
fossil fuel – energy sources like coal, oil, and natural gas
layer – one thickness lying over or under one another
urban – pertaining to cities
Fill in the following diagram.
Theory
1.
Criticism
A 2.
B 3.
Now answer the questions using your notes.
Global Warming
Summarize the text using your notes and diagram.
- 1: Earth's temperature is getting higher because of human activity.
- 2: Temperature of an important layer of the atmosphere is not getting higher.
- 3: Natural causes may be responsible for any changes in the Earth's temperature.
Listen again:
W1: We've all heard about the theory of global warming and how it's being caused by the activities of man. But something we don't hear a lot about are critics' theories against manmade global warming. Let's talk about those theories today.
First, I'll quickly go over the theory of global warming, although this will most likely be a review for most of you. The theory states that changes in the temperature of the Earth are the result of human activity – specifically, people burning fossil fuels. It says that burning them for energy causes the Earth's temperature to rise. This creates greenhouse gases that heat up the Earth.
M: So that means when we drive our cars and fly on airplanes, we're causing the Earth to get hotter?
W1: According to the theory, yes, But for critics against global warming, the answer to your question is not so clear. There are two reasons for this. First, the lower troposphere is not getting hotter. If there were global warming caused by greenhouse gases, scientists say that the temperature of the layer of the Earth's atmosphere… called the lower troposphere… should be increasing. It is clear that the land temperatures in some areas have gotten warmer, for many complex reasons. But the interesting thing is – over the last 23 years, which is how long we have measured it – for the last 23 years there have been no temperature increases in the lower troposphere. Yes Beth, did you have a question?
W2: Yeah. How could the land get warmer if the lower troposphere isn't getting warmer?
W1: To answer your question, critics contend that changes in land temperatures are happening in places where' urban areas are spreading out or where forests have been cut down.
M: Oh. Okay.
W1: The second criticism concerns the cause of temperature change. Scientists have studied changes in the Earth's climate that go back billions of years. These studies show that the Earth naturally gets warmer or cooler. The temperature changes in cycles. It is entirely possible that today, changes in temperature are the result of natural changes, not caused by human activity.
