El Nino and La Nina

Here’s what can happen when the surface of the equatorial Pacific gets just a little warmer: Thousands of people die as the weather changes from India to Florida. Some economies lose billions of dollars; others enjoy respite from weather-related losses. Prices of commodities ranging from nickel to coffee jolt skyward. Then when the waters cool, patterns shift, with areas previously spared often experiencing calamitous hurricanes, floods or drought, and others getting a break from such buffeting forces. The whole cycle is known as El Nino-Southern Oscillation. It is made up of El Nino, the Pacific’s warm phase; La Nina, the cold side; and a neutral phase in between. The whole thing tends to play itself out every two to seven years.

Early in 2017, forecasts called for another El Nino, after a stunning 2015 occurrence. By summer those expectations collapsed. The lack of El Nino actually removed a barrier to growth of Atlantic hurricanes, which contributed to a series of devastating storms including Harvey, Irma and Jose. In October, the U.S. Climate Prediction Center declared the presence of La Nina. That increases the chances for drought in parts of Brazil and Argentina and heavy rains in the coal mining regions of Australia. In the U.S., a mild winter is likely across the south and the east coast. This La Nina, however, is weak; the Australian Bureau of Meteorology doesn’t even recognize it. Weak events don’t always bring noticeable changes to the weather. By contrast, the last El Nino, the strongest since the record event of 1997-98, made a considerable impact. It reduced rainfall in the Indian monsoon, parching farmlands, and curbed production of cocoa in Ivory Coast, rice in Thailand and coffee in Indonesia. The 2015 El Nino was followed by La Nina in 2016.