[a习作temp] argument47[0607G-cheer小组]第五次作业 [复制链接]

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发表于 2007-2-15 18:18:57 |只看该作者 |倒序浏览

第五次作业
argument47

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.

The author claims that the sudden cooling in the earth in the mid-sixth century was caused by a volcanic eruption.To support this conclusion,the author cited some accounts that mention a dimming of the sun and cold temperatures at that time. Im addoition, the author points out the two possibilities that could cause the cooling and rules out one of them based on the extant historical records.However,this argument is based on poor assumptions.

Firstly, even if the accounts found in Asia and Europe are credible,it is not clear that whether the cooling is a world trend. Without accounts found in other continents recording the same or similar fact, the author cannot rule out the possibility that it is just a patial weahther alteration due to a volcanic eruption or a meteorite collision as the author tells.

Secondly, even if it is a worldwide cooling,the author fails to rule out other possibility that could cause the change in weather besides the volcanic eruption and meteorite collision.As we know ,the weather is affected by many factors.For example,Since the total population of living creature exerts great influence on the amount of carbon oxide,which absorps the energy of sunlight and keeps heat,thus the change in population would accordingly alter the weather.Without ruling out this and other factors,the assumption is dubious.

Thirdly, that no extant historical records of the time such a flash ,which is probably caused by a large volcanic eruption, does not rule out the possibilty that the volcanic eruption caused the cooling.Given the fact that the volcanic eruption do not necessarily cause the flash and the possiblity that people had not recorded the phenomenon and the possibility that the records maybe lost in the long history, the author cannot justify this assumption.

In sum, this argument is unconvincing as it stands.To strengthen it, the author must prove that all the mentioned records are credible and the cooling at that time is a world trend.In addition, the author must rule out other possible causes of the weather change.