argument47 【CSMY作文互改小组】第5次作业 -- 最近很头疼arg，帮忙看看问题在哪里吧

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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.

1。Record的可信度，和证明力
2。没有large meteorite colliding 不能说明volcanic eruption 就是原因
3。Volcanic eruption 不一定能导致cooling

The author claims that it is quite possible that volcanic eruption led to cooling in the earth, which is expected to be supported by the historical records he cited. However, these records are not intact enough and his reduction is illogical, leading to the unconvincing conclusion.

First of all, the historical evidences are limited. Even assuming these records are credible and concise, only the situation in Asia and Europe could not tell the global state at that time. In fact, the reliability is a problem. Maybe in other disappeared records, the descriptions were not the same. None records do not mean no occurrence. Moreover, the phenomenon mentioned in the surviving Asian records was blur without clear definition and confirmed conclusion; the author just speculate on the description, which should not be taken as evidence. The recorder probably failed to see the flash of light, because where the meteorite appeared was too far to been seen by the recorder. Or the recorder missed to recognize the light as the sign of meteorite collision if the sky was not clear or it is in the daytime. Therefore, the assertion on the nonexistence of meteorite collision is unfounded.

Second, the assumption that the two phenomenon -- volcanic eruption and large meteorite colliding – are mutually exclusive is questionable. Even the large meteorite were not responsible for the cooling, there were still other factors contributing to the low temperature other than volcanic. The cooling may be a result of sun activities, or other planet influence. Or the internal chemical and physical movement would be responsible for the appearance temperatures, like the earthquake or water circulation. Since the reasons of cooling would be more than volcanic eruption and meteorite colliding, ruling out the latter could not prove the former is the only one cause.  

Third, even there were huge volcanic eruptions at that time, no direct evidence is provided to manifest the direct effect of volcanic eruption. The cooling may occur before cooling, or it accompanied with the reducing temperature as effects of other causes, like internal movement, climate changing, and so on. On the other side, the temperatures might not reduce after a volcanic eruption. The matters in the eruption tended to be in high temperature which increased the earth’s temperature. The dust in the air might form a layer of protection for the earth to exchange the heat with the higher air. The erupted gas might be hot and remained above the earth which was like the warm. If so, the results would be completely contrary to the author assumes. Without profound evidences, it is too harsh for the author to make an inference.

In sum, the claim that a volcanic eruption led the cooling in the earth is an open question until the author provides more reliable and authoritative information to support his deduction. The information should include the records in other places, the possibility of the large meteorite collision, the factors of cooling and the effect of volcanic eruption.
觉得这篇不难，但限时写写得很烂，改了后还是觉得重点可能错了。麻烦帮忙看看。