47. 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.
In the argument, the writer concludes that the sudden cooling of earth was probably caused by a volcanic eruption. To support the conclusion, several facts are cited that either a huge volcanic eruption or a large meteorite colliding with Earth was capable of lowering global temperatures significantly; however, there are no extant historical records of a sudden flash created by large meteorite collision in the mid-sixth century, while a loud boom that would be consistent with a volcanic eruption is mentioned in some surviving Asian historical records. At first glance, the argument seems well organized and persuasive, whereas careful scrutiny reveals that it includes several logical flaws, and therefore is questionable.
To begin with, it is illogical that the writer assumes that a volcanic eruption and a large meteorite collision are the only two possible causes of the sudden decline of temperature in the mid-sixth century. Myriads of other factors, such as abnormal actions of the sun, conflagration of forests and ocean currents, might be attributable to the decrease of temperature. Without ruling out these possibilities, the writer could not draw a convincing conclusion.
In addition, even if we concede the writer’s assumption, the argument is still unpersuasive. The lack of extant historical records of a flash created by a large collision could not indicate that the event did not happen. On the one hand, maybe the historical records about the flash were ruined in a war, a fire or other bales, or still lie in some corner of immense historical materials. On the other hand, it is entirely possible that the collision happened in a desert area, such as the middle of Pacific, the Arctic, the Antarctic and so on, and people of that time did not observe it. Any of these scenarios, if true, would weaken the argument.
Moreover, the writer assumes that the loud boom mentioned was consistent with the volcanic eruption, and nevertheless does not provide adequate and clear evidences to support the assumption. It is very possible that the loud boom was caused by a large meteorite collision. What’s more, the volcanic eruption perhaps has happened before the sudden change of Earth’s temperature. In this case, the volcanic eruption would have no effects on the change of temperature. Therefore, lacking enough data and records, it is hasty for the writer to attribute the weather change in sixth-century mid to a volcanic eruption.
Accordingly, the argument suffers from several obvious fallacies which render it unconvincing as it stands. To strength the argument, further analysis and more substantial evidences are necessary. To bolster the conclusion, the writer should provide clear evidences to show that other possible factors have little influence on the sudden change of temperature. Furthermore, to better evaluate the writer’s claim, more information about a volcanic eruption and a large meteorite collision of that time also is needed.