El Niño or La Niña?

El Niño or La Niña?

If you get confused by these Spanish words for little boy and little girl, as they are applied to the weather, you are not alone! El Niño or La Niña apply to changing climatic conditions, but this is not necessarily to be confused with long-term climate change.

The Climate Prediction Center announced earlier this month that El Niño has begun and will last for the next eighteen months. It is a naturally occurring phenomenon caused by the changing temperature of the oceans near the equator. The temperatures vary with the strength of the trade winds. These changes, at least so far, are cyclical, though the length of each cycle varies from months to years.

The National Ocean Service, part of the National Oceanic and Atmospheric Administration, explains that in normal years, the trade winds blow west across the Pacific Ocean near the equator, moving warm water from South America to Asia. Cold water then upwells from the depths, full of phytoplankton, feeding schools of fish and up the food chain. But when the trade winds weaken, warm water is pushed east toward the west coast of the Americas. This is called an El Niño season. The Pacific jet stream moves south, causing warmer and dryer weather in the northern part of the US and Canada, and wetter weather than usual in the South.

When this weather pattern reverses itself, with trade winds blowing stronger toward Asia, and more upwelling of cold water in the Pacific, pushing the Gulf Stream northward, it is called La Niña. Wonderful for the fish, attracted by the nutrients brought closer to the ocean surface off the West Coast. Droughts beset the South, and heavy rain and flooding occur in Canada and the Pacific Northwest with colder winters in the northern states and a more severe hurricane season.

These weather patterns are natural. But because we have had several La Niña years in a row with weather effects that defy the norm, it is confusing. Last winter California had floods, while the Northeast did not have a particularly cold winter and the hurricane season was fairly mild. And wildfires are burning the boreal forest in Canada.

Unpredictability is the only predictable in our future.

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