ARGUMENT47 飞跃小组第四次作业 好难啊

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TOPIC: ARGUMENT47 - Scientists studying historical weather patterns have discovered that in the mid-sixth century, Earth suddenly became significantly cooler. Although few historical records survive from that time, some accounts found both in Asia and Europe mention a dimming of the sun and extremely cold temperatures. Either a huge volcanic eruption or a large meteorite colliding with Earth could have created a large dust cloud throughout Earth's atmosphere that would have been capable of blocking enough sunlight to lower global temperatures significantly. A large meteorite collision, however, would probably create a sudden bright flash of light, and no extant historical records of the time mention such a flash. Some surviving Asian historical records of the time, however, mention a loud boom that would be consistent with a volcanic eruption. Therefore, the cooling was probably caused by a volcanic eruption.
WORDS: 404          TIME: 0:31:25          DATE: 2007-2-27

Inn this memo, the author concludes that the cooling of earth was probably caused by a volcanic eruption (VE). To support the conclusion, the author points out that some accounts found both in Asia and Europe mention a dimming of the sun and extremely cold temperatures. The author also cites that a huge volcanic eruption or a large meteorite colliding (MC) with Earth could have created a large dust cloud throughout Earth's atmosphere that would have been capable of blocking enough sunlight to lower global temperature, however there is no such a flash record to show it is coursed by the MC. However the argument relies on a series of substantiated assumption.

First, no extant historical records of a flash does little indicate that a MC did not come to Earth. Perhaps, it is possible that MC came to Earth and a flash was occurred but not recorded by some reasons for example the flash is occurred during day time and it is difficult to see. So it is impossible to say that MC did not come because there is no flash.

Second, it is unbelievable to concludes that a loud boom in Asia is coursed by VE. First, a loud boom may be sent out by an Earth quake, but people recorded it as a sense of VE by mistake. Second, even though the VE have arrived on Earth, perhaps it dropped in the sea that will bring no dust cloud at all. So the author should not present that the cooling is caused by a VE without some more evidence.

Third, the cooling is caused by a dust cloud throughout Earth's atmosphere which block the sun light is uncertain if justify only by the evidence from author. First the author cites no evidence that a dust cloud will block the sun light, may be the sun light is strong enough to go through the dust. Second the author has no evidence that a lacking of sun light, the temputerature will go down. So the cooling is caused by the dust is unbelievable.

In sum, based on some unbelievable assumptions in this argument the conclusion is not well supported as it stands. To strengthen the conclusion, the author should show more evidence that the MC did not come to Earth but VE did. The author should also present more information that there is surly a dust cloud throughout Earth's atmosphere during that time.