El Nino is the name given to the mysterious and often unpredictable change
in the climate of the world. This strange 47 happens every five to eight
years.
It starts in the Pacific Ocean and is thought to be caused by a failure in
the trade winds(信风), which affects the ocean currents driven by these winds. As
the trade winds lessen in 48 , the ocean temperatures rise, causing the Peru
current flowing in from the east to warm up by as much as 5 °C.
The warming of the ocean has far-reaching effects. The hot, humid (潮湿的) air
over the ocean causes severe 49 thunderstorms. The rainfall is increased across
South America, 50 floods to Peru. In the West Pacific, there are droughts
affecting Australia and Indonesia. So while some parts of the world prepare for
heavy rains and floods, other parts face drought, poor crops and 51.
El Nino usually lasts for about 18 months. The 1981-83 El Nino brought the
most 52 weather in modern history. Its effect was worldwide and it left more
than 2,000 people dead and caused over eight billion pounds 53 of damage. The
1990 El Nino lasted until June 1995. Scientists 54 this to be the longest El
Nino for 2,000 years.
Nowadays, weather experts are able to forecast when an El Nino will 55 ,
but they are still not 56 sure what leads to it or what affects how strong it
will be.