Please read the following article and find out what role ElNi?o and La Ni?a play.
请阅读以下文章,看一看厄尔尼诺和拉尼娜现象所起的作用。
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During the droughts of 1997 and 1998, which were linked to ElNi?o, an irregular warming of the Pacific Ocean, 39,000 square kilometres of Amazonian forest were burned by such fires.
However, when surface waters are warm (as during an elni? O), they do not allow the colder, deeper currents to upwell and effectively block the flow of life-sustaining nutrients.