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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: 488          TIME: 0:29:45          DATE: 2006-8-19

The author recommends that the cooling discovered in the mid-sixth century was probably caused by a volcanic eruption, based on the evidence survived and some reasoning of the author's. However, the recommendation of the argument is not persuasive, for that a careful examination exposed some flaws in some aspects.

First, the author problematic concludes that the extremely cooling are resulted from the lack of sunlight, for that he mentions the evidence found in Asia and Europe indicate a dimming of the sun and extremely cold temperatures. Since, the evidence relevant found is very rare, the exist evidence is not strongly support such relationship between the dimming of the sun and extremely cooling. For one hand, whether the dimming of the sun and extremely cooling were happened correspondingly is unclearly, it is possible that the extremely cold temperatures was occured after the dimming of the sun, then the dimming of the sun is certainly not the cause of the cooling. For the other hand, there may be evidence that was destroyed to present no dimming of the sun but extremely cold temperatures, which is controversial with the conclusion. Thus, the conclusion are unconvincing.

Moreover, even the conclusion are cogent, that the extremely could temperatures was ascribed to the dimming of the sun, the reasoning that the meteorite collision was not the cause doubtful. Because the fact that no extant historical records of the flash does not surely exhibit the claim that no flash was occured, it is equally possible that the record of the flash is not preserved well and damaged thus none survived, and that the flash did occur without observation, leading to no record. As a result, the possibility is completely persuasive that the cooling was result from a collision of a meteorite.

Further more, the surviving Asian historical records of a loud boom are not surely substantiate the conclusion that the cooling was cased by a volcanic eruption. Though a loud boom was mentioned in the record that would be consistent with a volcanic eruption, no information of the time the two factors happened is cited, if the boom was happened after the volcanic eruption, the cause-and-effect relationship between them is soundly doubtful. Besides, perhaps, the boom was resulted from other reasons that the records are kept uncovered. Hence, to claim that the cooling was probably caused by a volcanic eruption is questionable.

Apart from what had been discussed above, other possibility contributing to the cooling should be taken into account, such as a sudden and dramatic climate change.

TO sum up, the author invalid recommends the cooling in the mid-sixth century was probably cased by a volcanic eruption, based on the uncertain and inefficient evidence. Therefore, further information about the reason of dimming of the sun and the record of the meteorite collision and volcanic eruption should be provided and the other factors caused the cooling should be taken into account to make the argument more cogent.