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47Scientists 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.
In this argument, the arguer concludes that the cooling in the mid-sixth century was probaly caused by a volcanic eruption. This conclusion rests on several unsubstantiated assumptions, and therefore unpersuasive as it stands.
First of all, the conclusion relies on an assumption that a huge volcanic eruption and a large meteorite colliding are the only available ways to cause the earth cold. However, a huge volcanic eruption and a large meteorite colliding are not necessary mutually-exclusive alternatives. It is more likely that other factors must also contribute to the problem. For example, may be some huge earthquake also created a large dust cloud. If so, just attributing the cooling of the earth to volcanic eruption and meteorite colliding is not convincing.
Secondly, the evidences the author provided is insufficient to support the assumption that it is not the large meteorite colliding cause the weather cooler. Mere fact that no extant historical records of the time mention a sudden bright flash of light and a loud boom recorded would be consistent with a volcanic eruption is insufficient to establish this assumption, No record does not mean no bright flash. It is high possible that no people record the flash or we do not discover the records. And also maybe the huge meteorite colliding happened in somewhere no people residented. For instance, the colliding maybe happened in arctic, and no people saw such a big flash. Without ruling out these and other alternative factors, the author can not confidently convince us that no large meteorite colliding happened in that time.
Finally, even assuming that no large meteorite colliding happened in that time, the author also fails to provide adequate evidence to persuade us that a volcanic eruption cause the cooling. Though the author indicates some evidence to show that there was a loud boom which may be caused by a volcanic eruption, it can not prove the conclusion. Whether the volcanic eruption large enough to cause a huge dust cloud throughout the Earth's atmosphere or not is unknown. Moreover, even if the volcanic eruption large did bring about a dust cloud, the author also fails to justify the assumption that a large dust cloud would have been capable of blocking enough sunlight to lower global temperatures significantly. If the dust cloud made no big effect on blocking sunlight, these scenarios must serve to undermine the conclusion above.
To sum up, this argument is not persuasive as it stands. To strengthen the conclusion, the author must provide more evidence to support the assumption that no a large meteorite colliding happened in that time, and no alternative factors that give rise to the cooling. |
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