"Nobody really knows" was Donald Trump’s assessment of man-made global warming, in an interview on December 11th. 【F1】 As far as

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问题     "Nobody really knows" was Donald Trump’s assessment of man-made global warming, in an interview on December 11th. 【F1】 As far as the atmosphere is concerned, that puts him at odds with most scientists who have studied the matter. They do know that the atmosphere is warming, and they also know by how much. But turn to the sea and Mr. Trump has a point. Though the oceans are warming too, climatologists readily admit that they have only a rough idea how much heat is going into them, and how much is already there.
    Many suspect that the heat capacity of seawater explains the climate pause of recent years, in which the rate of atmospheric warning has slowed. 【F2】 But without decent data, it is hard to be sure to what extent the oceans are acting as a heat sink that damps the temperature rise humanity is visiting upon the planet—and, equally important, how long they can keep that up.
    This state of affairs will change, though, if a project described by Robert Tyler and Terence Sabaka to a meeting of the American Geophysical Union, held in San Francisco this week, is successful. Dr Tyler and Dr Sabaka, who work at the Goddard Space Flight Centre, observe that satellites can detect small changes in Earth’s magnetic field induced by the movement of water. They also observe that the magnitude of such changes depends on the water’s temperature all the way down to the ocean floor. That, they think, opens a window into the oceans which has, until now, been lacking. To measure things in the deep sea almost always requires placing instruments there. 【F3】 The supply of oceanographic research vessels, though, is limited, and even the addition in recent years of several thousand "Argo" probes (floating robots that roam the oceans and are capable of diving to a depth of 2,000 metres) still leaves ocean temperatures severely under-sampled.
    Satellites, however, can look at the whole ocean—and, if they are properly equipped, can plot ways in which Earth’s magnetic field is deflected by seawater. This deflection happens because seawater is both electrically conductive and always on the move. Crucially, saltwater’s conductivity increases with its temperature. This means the deflection increases, too. 【F4】 And since the magnetic field originates from within Earth, it penetrates the whole ocean, from bottom to top. So any heat contributes to the deflection.
    【F5】 All this means that, if you know where and how ocean water is displaced, the changes in the magnetic field, as seen from a satellite, will tell you the heat content of that water. Dr Tyler and Dr Sabaka therefore built a computer model which tried this approach on one reasonably well-understood form of oceanic displacement, the twice-daily tidal movement caused by the gravitational attraction of the moon.
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答案但是因缺乏确切的数据,很难确定对于人类在地球上的活动所造成的气温上升,海洋的热沉效应有多大,同样重要的是,海洋的这种功能还能维持多久。

解析 本句为复合句。without decent data是介词短语,主干句的句型为it is hard to do sth., 主语为it, is为系动词,表语为hard to be sure…,其中sure引导了两个宾语从句,由and连接。第一个为省略了that的宾语从句,其主语为the oceans,谓语为are acting…as…(作为……发挥作用),as的宾语为a heat sink,that引导的定语从句修饰其先行词sink。该定语从句的谓语为damps,宾语为the temperature rise;sure的第二个宾语从句由how引导,其主语为they谓语为damps,宾语为that。其中equally important为插入语。
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