Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about an often-overlooked contributor to climate change: methane. Unlike carbon dioxide, which stays in the atmosphere for centuries, methane has a much shorter lifespan, but it's far more efficient at trapping heat. In fact, over a 20-year period, methane's global warming potential is over 80 times that of carbon dioxide. So where does it come from? Natural sources include wetlands and termites, but human activities dominate. The largest human-made source is agriculture, specifically livestock—cows and sheep produce methane through their digestion. Another major source is fossil fuel extraction; when we drill for oil and gas, methane often leaks into the atmosphere. Landfills are also significant, as decomposing organic waste releases methane. The good news is that because methane doesn't persist long, reducing emissions now can have a rapid impact on slowing global warming. So policies targeting methane may offer a quicker win than those focused solely on CO2.
❓ 質問 What is the main point the professor makes about methane?
A. A) Methane remains in the atmosphere longer than carbon dioxide.
B. B) Methane is a more potent greenhouse gas but has a shorter atmospheric lifetime.
C. C) Methane emissions come only from natural sources like wetlands.
D. D) Reducing methane emissions has little effect on global warming.
✅ 正解
B) Methane is a more potent greenhouse gas but has a shorter atmospheric lifetime.
TOEFL Listening Tips
Skim the questions first to predict the content
Watch for signal words in lectures and conversations (however, actually, in fact)
For main idea questions, focus on the beginning; for detail questions, focus on examples and data
For attitude questions, pay attention to the speaker's tone and word choice
Take notes on keywords; don't try to write down every word
