gre考试阅读真题解析(A)
<p> <span word="Aided">Aided</span> <span word="by">by</span> <span word="the">the</span> <span word="recent">recent</span> <span word="ability">ability</span> <span word="to">to</span> <span word="analyze">analyze</span> <span word="samples">samples</span> <span word="of">of</span> <span word="air">air</span> <span word="trapped">trapped</span> <span word="in">in</span> <span word="glaciers">glaciers</span>, <span word="scientists">scientists</span> <span word="now">now</span> <span word="have">have</span> <span word="a">a</span> <span word="clearer">clearer</span> <span word="idea">idea</span> <span word="of">of</span> <span word="the">the</span> <span word="relationship">relationship</span> <span word="between">between</span> <span word="atmospheric">atmospheric</span> <span word="composition">composition</span> <span word="and">and</span> <span word="global">global</span> <span word="temperature">temperature</span> <span word="change">change</span> <span word="over">over</span> <span word="the">the</span> <span word="past">past</span> 160,000 <span word="years">years</span>. <span word="In">In</span> <span word="particular">particular</span>, <span word="determination">determination</span> <span word="of">of</span> <span word="atmospheric">atmospheric</span> <span word="composition">composition</span> <span word="during">during</span> <span word="periods">periods</span> <span word="of">of</span> <span word="glacial">glacial</span> <span word="expansion">expansion</span> <span word="and">and</span> <span word="retreat">retreat</span> <span word="is">is</span> <span word="possible">possible</span> <span word="using">using</span> <span word="data">data</span> <span word="from">from</span> <span word="the">the</span> 2,000 <span word="meter">meter</span> <span word="Vostok">Vostok</span> <span word="ice">ice</span> <span word="core">core</span> <span word="drilled">drilled</span> <span word="in">in</span> <span word="Antarctica">Antarctica</span>. <span word="The">The</span> <span word="technique">technique</span> <span word="involved">involved</span> <span word="is">is</span> <span word="similar">similar</span> <span word="to">to</span> <span word="that">that</span> <span word="used">used</span> <span word="in">in</span> <span word="analyzing">analyzing</span> <span word="cores">cores</span> <span word="of">of</span> <span word="marine">marine</span> <span word="sediments">sediments</span>, <span word="where">where</span> <span word="the">the</span> <span word="ratio">ratio</span> <span word="of">of</span> <span word="the">the</span> <span word="two">two</span> <span word="common">common</span> <span word="isotopes">isotopes</span> <span word="of">of</span> <span word="oxygen">oxygen</span>, 18<span word="O">O</span> <span word="and">and</span> 16<span word="O">O</span>, <span word="accurately">accurately</span> <span word="reflects">reflects</span> <span word="past">past</span> <span word="temperature">temperature</span> <span word="changes">changes</span>. <span word="Isotopic">Isotopic</span> <span word="analysis">analysis</span> <span word="of">of</span> <span word="oxygen">oxygen</span> <span word="in">in</span> <span word="the">the</span> <span word="Vostok">Vostok</span> <span word="core">core</span> <span word="suggests">suggests</span> <span word="mean">mean</span> <span word="global">global</span> <span word="temperature">temperature</span> <span word="fluctuations">fluctuations</span> <span word="of">of</span> <span word="up">up</span> <span word="to">to</span> 10 <span word="degrees">degrees</span> <span word="centigrade">centigrade</span> <span word="over">over</span> <span word="the">the</span> <span word="past">past</span> 160,000 <span word="years">years</span>.</p><p> <span word="Data">Data</span> <span word="from">from</span> <span word="the">the</span> <span word="Vostok">Vostok</span> <span word="core">core</span> <span word="also">also</span> <span word="indicate">indicate</span> <span word="that">that</span> <span word="the">the</span> <span word="amount">amount</span> <span word="of">of</span> <span word="carbon">carbon</span> <span word="dioxide">dioxide</span> <span word="has">has</span> <span word="fluctuated">fluctuated</span> <span word="with">with</span> <span word="temperature">temperature</span> <span word="over">over</span> <span word="the">the</span> <span word="same">same</span> <span word="period">period</span>: <span word="the">the</span> <span word="higher">higher</span> <span word="the">the</span> <span word="temperature">temperature</span>, <span word="the">the</span> <span word="higher">higher</span> <span word="the">the</span> <span word="concentration">concentration</span> <span word="of">of</span> <span word="carbon">carbon</span> <span word="dioxide">dioxide</span> <span word="and">and</span> <span word="the">the</span> <span word="lower">lower</span> <span word="the">the</span> <span word="temperature">temperature</span>, <span word="the">the</span> <span word="lower">lower</span> <span word="the">the</span> <span word="concentration">concentration</span>. <span word="Although">Although</span> <span word="change">change</span> <span word="in">in</span> <span word="carbon">carbon</span> <span word="dioxide">dioxide</span> <span word="content">content</span> <span word="closely">closely</span> <span word="follows">follows</span> <span word="change">change</span> <span word="in">in</span> <span word="temperature">temperature</span> <span word="during">during</span> <span word="periods">periods</span> <span word="of">of</span> <span word="deglaciation">deglaciation</span>, <span word="it">it</span> <span word="apparently">apparently</span> <span word="lags">lags</span> <span word="behind">behind</span> <span word="temperature">temperature</span> <span word="during">during</span> <span word="periods">periods</span> <span word="of">of</span> <span word="cooling">cooling</span>. <span word="The">The</span> <span word="correlation">correlation</span> <span word="of">of</span> <span word="carbon">carbon</span> <span word="dioxide">dioxide</span> <span word="with">with</span> <span word="temperature">temperature</span>, <span word="of">of</span> <span word="course">course</span>, <span word="does">does</span> <span word="not">not</span> <span word="establish">establish</span> <span word="whether">whether</span> <span word="changes">changes</span> <span word="in">in</span> <span word="atmospheric">atmospheric</span> <span word="composition">composition</span> <span word="caused">caused</span> <span word="the">the</span> <span word="warming">warming</span> <span word="and">and</span> <span word="cooling">cooling</span> <span word="trends">trends</span> <span word="or">or</span> <span word="were">were</span> <span word="caused">caused</span> <span word="by">by</span> <span word="their">their</span>.</p><p> <span word="The">The</span> <span word="correlation">correlation</span> <span word="between">between</span> <span word="carbon">carbon</span> <span word="dioxide">dioxide</span> <span word="and">and</span> <span word="temperature">temperature</span> <span word="throughout">throughout</span> <span word="the">the</span> <span word="Vostok">Vostok</span> <span word="record">record</span> <span word="is">is</span> <span word="consistent">consistent</span> <span word="and">and</span> <span word="predictable">predictable</span>. <span word="The">The</span> <span word="absolute">absolute</span> <span word="temperature">temperature</span> <span word="changes">changes</span>, <span word="however">however</span>, <span word="are">are</span> <span word="from">from</span> 5 <span word="to">to</span> 14 <span word="times">times</span> <span word="greater">greater</span> <span word="than">than</span> <span word="would">would</span> <span word="be">be</span> <span word="expected">expected</span> <span word="on">on</span> <span word="the">the</span> <span word="basis">basis</span> <span word="of">of</span> <span word="carbon">carbon</span> <span word="dioxides">dioxides</span> <span word="own">own</span> <span word="ability">ability</span> <span word="to">to</span> <span word="absorb">absorb</span> <span word="infrared">infrared</span> <span word="radiation">radiation</span>, <span word="or">or</span> <span word="radiant">radiant</span> <span word="heat">heat</span>. <span word="This">This</span> <span word="reaction">reaction</span> <span word="suggests">suggests</span> <span word="that">that</span>, <span word="quite">quite</span> <span word="aside">aside</span> <span word="from">from</span> <span word="changes">changes</span> <span word="in">in</span> <span word="heat">heat</span>-<span word="trapping">trapping</span> <span word="gases">gases</span>, <span word="commonly">commonly</span> <span word="known">known</span> <span word="as">as</span> <span word="greenhouse">greenhouse</span> <span word="gases">gases</span>, <span word="certain">certain</span> <span word="positive">positive</span> <span word="feedbacks">feedbacks</span> <span word="are">are</span> <span word="also">also</span> <span word="amplifying">amplifying</span> <span word="the">the</span> <span word="temperature">temperature</span> <span word="change">change</span>. <span word="Such">Such</span> <span word="feedbacks">feedbacks</span> <span word="might">might</span> <span word="involve">involve</span> <span word="ice">ice</span> <span word="on">on</span> <span word="land">land</span> <span word="and">and</span> <span word="sea">sea</span>, <span word="clouds">clouds</span>, <span word="or">or</span> <span word="water">water</span> <span word="vapor">vapor</span>, <span word="which">which</span> <span word="also">also</span> <span word="absorb">absorb</span> <span word="radiant">radiant</span> <span word="heat">heat</span> .</p>
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