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https://forum.chasedream.com/thread-910116-1-1.html
SCIENTIFIC AMERICAN
February 2007
Volume 296, Issue 2
https://www.scientificamerican.com/magazine/sa/2007/02-01/
P2 “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
关于ice age时的甲烷，哪个说法是对的?选可以用气泡中甲烷的含量发现，ice age开始前，甲烷浓度下降，ice age结束后，浓度上升
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.
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......
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.
Similar climate scenarios may have occurred during other periods of the earth’s history, particularly at mass extinction events, such as the Permian-Triassic boundary (250 million years ago) and the Triassic-Jurassic boundary (200 million years ago). Extremely high atmospheric carbon dioxide concentrations as well as rising temperatures could have resulted in a dramatic increase in vegetation biomass. Such global warming periods could have been accompanied by a massive release of methane from vegetation and by more heating. Though speculative, the assumption that emissions may have been as much as 10 times higher than at present is not totally unreasonable. If this is so, methane emissions from vegetation, in addition to emissions of the gas from wetlands and perhaps from the seafloor, could be envisaged as a driving force in historic climate change.
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发表于 2018-12-24 21:12:04
