gre考试阅读真题解析(A)
<p> <span word="It">It</span> <span word="has">has</span> <span word="been">been</span> <span word="known">known</span> <span word="for">for</span> <span word="many">many</span> <span word="decades">decades</span> <span word="that">that</span> <span word="the">the</span> <span word="appearance">appearance</span> <span word="of">of</span> <span word="sunspots">sunspots</span> <span word="is">is</span> <span word="roughly">roughly</span> <span word="periodic">periodic</span>, <span word="with">with</span> <span word="an">an</span> <span word="average">average</span> <span word="cycle">cycle</span> <span word="of">of</span> <span word="eleven">eleven</span> <span word="years">years</span>. <span word="Moreover">Moreover</span>, <span word="the">the</span> <span word="incidence">incidence</span> <span word="of">of</span> <span word="solar">solar</span> <span word="flares">flares</span> <span word="and">and</span> <span word="the">the</span> <span word="flux">flux</span> <span word="of">of</span> <span word="solar">solar</span> <span word="cosmic">cosmic</span> <span word="rays">rays</span>, <span word="ultraviolet">ultraviolet</span> <span word="radiation">radiation</span>, <span word="and">and</span> <span word="x">x</span>-<span word="radiation">radiation</span> <span word="all">all</span> <span word="vary">vary</span> <span word="directly">directly</span> <span word="with">with</span> <span word="the">the</span> <span word="sunspot">sunspot</span> <span word="cycle">cycle</span> . <span word="But">But</span> <span word="after">after</span> <span word="more">more</span> <span word="than">than</span> <span word="a">a</span> <span word="century">century</span> <span word="of">of</span> <span word="investigation">investigation</span>, <span word="the">the</span> <span word="relation">relation</span> <span word="of">of</span> <span word="these">these</span> <span word="and">and</span> <span word="other">other</span> <span word="phenomena">phenomena</span>, <span word="known">known</span> <span word="collectively">collectively</span> <span word="as">as</span> <span word="the">the</span> <span word="solar">solar</span>-<span word="activity">activity</span> <span word="cycle">cycle</span>, <span word="to">to</span> <span word="terrestrial">terrestrial</span> <span word="weather">weather</span> <span word="and">and</span> <span word="climate">climate</span> <span word="remains">remains</span> <span word="unclear">unclear</span>. <span word="For">For</span> <span word="example">example</span>, <span word="the">the</span> <span word="sunspot">sunspot</span> <span word="cycle">cycle</span> <span word="and">and</span> <span word="the">the</span> <span word="allied">allied</span> <span word="magnetic">magnetic</span>-<span word="polarity">polarity</span> <span word="cycle">cycle</span> <span word="have">have</span> <span word="been">been</span> <span word="linked">linked</span> <span word="to">to</span> <span word="periodicities">periodicities</span> <span word="discerned">discerned</span> <span word="in">in</span> <span word="records">records</span> <span word="of">of</span> <span word="such">such</span> <span word="variables">variables</span> <span word="as">as</span> <span word="rainfall">rainfall</span>, <span word="temperature">temperature</span>, <span word="and">and</span> <span word="winds">winds</span>. <span word="Invariably">Invariably</span>, <span word="however">however</span>, <span word="the">the</span> <span word="relation">relation</span> <span word="is">is</span> <span word="weak">weak</span>, <span word="and">and</span> <span word="commonly">commonly</span> <span word="of">of</span> <span word="dubious">dubious</span> <span word="statistical">statistical</span> <span word="significance">significance</span>.</p><p> <span word="Effects">Effects</span> <span word="of">of</span> <span word="solar">solar</span> <span word="variability">variability</span> <span word="over">over</span> <span word="longer">longer</span> <span word="terms">terms</span> <span word="have">have</span> <span word="also">also</span> <span word="been">been</span> <span word="sought">sought</span>. <span word="The">The</span> <span word="absence">absence</span> <span word="of">of</span> <span word="recorded">recorded</span> <span word="sunspot">sunspot</span> <span word="activity">activity</span> <span word="in">in</span> <span word="the">the</span> <span word="notes">notes</span> <span word="kept">kept</span> <span word="by">by</span> <span word="European">European</span> <span word="observers">observers</span> <span word="in">in</span> <span word="the">the</span> <span word="late">late</span> <span word="seventeenth">seventeenth</span> <span word="and">and</span> <span word="early">early</span> <span word="eighteenth">eighteenth</span> <span word="centuries">centuries</span> <span word="has">has</span> <span word="led">led</span> <span word="some">some</span> <span word="scholars">scholars</span> <span word="to">to</span> <span word="postulate">postulate</span> <span word="a">a</span> <span word="brief">brief</span> <span word="cessation">cessation</span> <span word="of">of</span> <span word="sunspot">sunspot</span> <span word="activity">activity</span> <span word="at">at</span> <span word="that">that</span> <span word="time">time</span> ). <span word="The">The</span> <span word="Maunder">Maunder</span> <span word="minimum">minimum</span> <span word="has">has</span> <span word="been">been</span> <span word="linked">linked</span> <span word="to">to</span> <span word="a">a</span> <span word="span">span</span> <span word="of">of</span> <span word="unusual">unusual</span> <span word="cold">cold</span> <span word="in">in</span> <span word="Europe">Europe</span> <span word="extending">extending</span> <span word="from">from</span> <span word="the">the</span> <span word="sixteenth">sixteenth</span> <span word="to">to</span> <span word="the">the</span> <span word="early">early</span> <span word="nineteenth">nineteenth</span> <span word="centuries">centuries</span>. <span word="The">The</span> <span word="reality">reality</span> <span word="of">of</span> <span word="the">the</span> <span word="Maunder">Maunder</span> <span word="minimum">minimum</span> <span word="has">has</span> <span word="yet">yet</span> <span word="to">to</span> <span word="be">be</span> <span word="established">established</span>, <span word="however">however</span>, <span word="especially">especially</span> <span word="since">since</span> <span word="the">the</span> <span word="records">records</span> <span word="that">that</span> <span word="Chinese">Chinese</span> <span word="naked">naked</span>-<span word="eye">eye</span> <span word="observers">observers</span> <span word="of">of</span> <span word="solar">solar</span> <span word="activity">activity</span> <span word="made">made</span> <span word="at">at</span> <span word="that">that</span> <span word="time">time</span> <span word="appear">appear</span> <span word="to">to</span> <span word="contradict">contradict</span> <span word="it">it</span>. <span word="Scientists">Scientists</span> <span word="have">have</span> <span word="also">also</span> <span word="sought">sought</span> <span word="evidence">evidence</span> <span word="of">of</span> <span word="long">long</span>-<span word="term">term</span> <span word="solar">solar</span> <span word="periodicities">periodicities</span> <span word="by">by</span> <span word="examining">examining</span> <span word="indirect">indirect</span> <span word="climatological">climatological</span> <span word="data">data</span>, <span word="such">such</span> <span word="as">as</span> <span word="fossil">fossil</span> <span word="records">records</span> <span word="of">of</span> <span word="the">the</span> <span word="thickness">thickness</span> <span word="of">of</span> <span word="ancient">ancient</span> <span word="tree">tree</span> <span word="rings">rings</span>. <span word="These">These</span> <span word="studies">studies</span>, <span word="however">however</span>, <span word="failed">failed</span> <span word="to">to</span> <span word="link">link</span> <span word="unequivocally">unequivocally</span> <span word="terrestrial">terrestrial</span> <span word="climate">climate</span> <span word="and">and</span> <span word="the">the</span> <span word="solar">solar</span>-<span word="activity">activity</span> <span word="cycle">cycle</span>, <span word="or">or</span> <span word="even">even</span> <span word="to">to</span> <span word="confirm">confirm</span> <span word="the">the</span> <span word="cycles">cycles</span> <span word="past">past</span> <span word="existence">existence</span>.</p>
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