然后说了哪些产品更不容易被退货:打折商品、familiar products bought in unfamiliar distribution channels, etc. 而unfamiliar/new products不管是通过unfamiliar 还是familiar distribution channel都不会更不容易被退货。(有题)
v5: 有一篇讲methane甲烷,沼气,说它attribute to global warming 然后就展开。说到了vegetation和global warming的关系。第一段讲特别热和特别冷的时期这个methane呈现出的一些变化特征。然后科学家惊讶的发现海底也有methane但是它并不是某个特定时期global warming的cause...最后一段是说虽然vegetation 也会产生methane,但并不是减少植被覆盖就可以降低这种methane的密度,因为blabla......
V3甲烷那篇,还有题问suggest what of the sendiments in the sea? 还有题问忘了是文中提到的植被的减少还是增加的后果(反正是导致产生了很多甲烷),我选的是end of ice age(仅供参考,需要考时看清题目具体分析)(760)
v4:
1P说甲烷和二氧化碳一样是一种温室气体;也会造成global warming。列举了造成大气中M物质增加的原因,如燃烧石化燃料等。fuel fossil burn, fire and other.(有题考这段的作用,我认为是提供背景资料)
2P “Surprisingly”(转折)科学家发现植物plant也会释放M,提出如卫星空照的证据,说热带地区因为有较密集的丛林tropical forest,所以大气中的M特别集中。The article listed two studys to demonstrate that the plants really emit the methane.
Methane, Plants and Climate Change
The surprising recent finding that living plants produce methane does not throw doubt on the cause of global warming. Human activities—not plants—are the source of the surge in this and other greenhouse gases
By Frank Keppler and Thomas Röckmann
Our findings would explain a trend that has puzzled climate scientists for years: fluctuations in methane levels in parallel with changes in global temperatures. Ice cores serve as natural archives that store information about atmospheric composition and climate variability going back almost a million years. Tiny bubbles of air trapped in the ice reveal the relative concentrations of atmospheric gases in the past [see box on next page]. We see in the ice cores, for example, that variations of past carbon dioxide levels are closely linked to changes in global temperatures. During ice ages, carbon dioxide concentrations are low; during warm spells, levels increase.
In general, methane concentrations follow the same trend as carbon dioxide, but the reason has been unclear. Scientists have tried to use models of wetlands (the only major natural source of methane previously believed to exist) to reconstruct the curious variations of past methane levels. Yet they found it difficult to reproduce the reported differences in atmospheric methane levels between glacial and interglacial periods
取样中有小气泡含有S(又一个不认识的单词)。。。。可能是说随着冰河入到海洋,海底也沉积了很多M,上一个冰河时期的结束可能就是这些储存在海底的M被释放的结果。但是证据显示海底大概四万年都没有剧烈变动,所以这个应该不是导致冰河期结束的原因。推测应该是植物大量的繁衍,释放出M,导致平均气温越来越高才使得冰河期结束。
第二段,说其实Plant虽然会吸收carbon减少温室效应但是也是会排放这个methane的,从而解释了一个几千年前的一个现象,和Ice有关。提到了什么sediment并没有引起什么的巨变,而是一直保持stable的状态。二段中间一直到最后是重点,有两题,而且问得很集中,其中一题是问sediment的,答案就是并没有一起什么巨变这一个。
Another explanation that has been suggested involves the gas in a form known as methane hydrates [see “Flammable Ice,” by Erwin Suess, Gerhard Bohrmann, Jens Greinert and Erwin Lausch; Scientific American, November 1999]. These develop at high pressure, such as that found on the ocean floor. An unknown but possibly very large quantity of methane is trapped in this form in ocean sediments. The sudden release of large volumes of methane from these sediments into the atmosphere has been suggested as a possible cause for rapid global warming events in the earth’s distant past. Yet recent results from polar ice core studies show that marine methane hydrates were stable at least over the past 40,000 years, indicating that they were not involved in the abrupt increases of atmospheric methane during the last glacial cycle.
We know that terrestrial vegetation is very sensitive to environmental changes, and thus the total amount of vegetation on the planet varies as the climate cools down and warms up during glacial cycles. In light of our findings, such variations should now be seriously considered as a possible cause of declines in methane levels during glacial periods and rises during the interglacials. During the last glacial maximum—around 21,000 years ago—the plant growth of the Amazon forests was only half as extensive as today, and tropical vegetation might thus have released much less methane. Since that time, global surface temperature and carbon dioxide concentrations have risen, leading to enhanced plant growth and, we would expect, to more and more methane released from vegetation. 作者: 葡萄123 时间: 2019-9-17 16:36
ヾ(◍°∇°◍)ノ゙谢谢!作者: chloeuw 时间: 2019-9-17 21:31
Passage 2 甲烷和PTEM
第1段讲到在55million years ago 的Proterozoic 末期,地球温度迅速上升,carbon 12与carbon13 的isotope 比值发生了剧烈的变化,这一时期被称之为PETM,该变化与methane 的增加有关。
第2段,甲烷主要来自于有机物的分解。其hydrate 的形式被认为与PETM 有关,Methane hydrate 是一种冰状体形成于低温条件下例如tundra和一些大陆架的海底沉淀中。其所包含的甲烷含量及高,在当今被认为是天然气的有效替代。
第3段,Methane hydrate 因为压力和温度的限制,只存在某些特定的情境中。发现大陆架的一些地带在被冰层封闭的生物体释放该物质。但具体如何释放,及如何会达到今天所发现的量是一个open question。
第4段,具体有几种推测的机制。一是海底温度上升,促使其释放甲烷,甲烷到空气中,加剧气候变暖,形成滚雪球的效应,但是 初为什么会气候上升是个疑问。同样的,怀疑是ocean circulation 将暖流带到了该区域中造成释放,但为什么会有circulation 也无法解答。也有认为是landslide 造成大陆架某些地方受影响,释放甲烷,随后促进全球变暖,但要求造成全球的速度需很快才行