听力音频：
L1
讲座
1. What is the lecture mainly about?
The significance of the Sun’s cycles of magnetic activity
Consequences of gradual changes in the global climate
Explanations for a year of very unusual weather
An example of successfully predicting extreme weather events
2. What point does the professor make about the unusual weather in the northeastern United States in 1816?
It followed an especially cold winter.
Its clod periods alternated with exceptionally hot ones.
It contrasted with the fairly normal weather that the rest of the world experienced that year.
It had a severe impact on the agricultural economy of that region.
3. Why does the professor mention Thomas Jefferson?
To cite a contemporary account of the weather written in 1816
To explain the origin of a theory about the Sun’s magnetic cycles
To give Jefferson credit for sending explorers to carefully study volcanoes
To show how the strange weather events affected Jefferson’s presidency
4. The professor talks about a theory that the unusual weather in 1816 was primarily caused by the Sun’s low magnetic activity. What does he imply about the theory?
It is no longer as widely believed as it was in the past.
It is the theory that he and most other experts accept.
It cannot be true, since the Sun’s magnetic activity was not low in 1816.
It was proposed so recently that most experts have not yet been able to consider it.
5. According to the professor, how can volcanic eruptions affect the weather in faraway places?
By altering the wind patterns high in the atmosphere
By sending into the stratosphere particles that block sunlight
By creating what is called the greenhouse effect
By accelerating the formation of rain clouds over a large area of the world
6. What does the professor imply about a recent study of growth rings in trees?
He intends to use it in future research on the effects of the Sun’s magnetism.
He feels that it did not properly consider all the significant factors.
He believes that its results support the volcanic theory.
He does not have confidence in the methods used by the researchers.
