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How will climate change affect our back-and-forth La Niña, El Niño weather patterns?

Conrad Swanson, The Seattle Times on

Published in Science & Technology News

This is a simple question with perhaps not so simple an answer.

Scientists do expect rising global temperatures to influence the weather patterns known as La Niña and El Niño — but just how strong that influence will be remains unclear. Much will depend on the many other variables that play a part in our daily weather and long-term climate.

Those factors include natural variability, competing weather patterns, location, geography, and even the chemistry of the ocean.

What are El Niño and La Niña anyway?

Before we dive into the nuance, let's start with the basics.

During El Niño years, warm Pacific Ocean waters near the equator push warm, tropical air into our region. The pattern is most noticeable in the winter months and generally means a warmer, drier season.

 

We're currently in an El Niño year, so you might be noticing some of those effects. Mountain snowpack is down across the board (though there are other factors at play as well). Seattle had its warmest December on record, followed by another record-setting warm week in January.

The pattern is waning now, though, and meteorologists expect La Niña to take its place.

Think of La Niña as the mirror image to El Niño. Cool ocean waters in the tropics push colder air into the Pacific Northwest. Again, most noticeable during the winter months, it generally makes for a colder and wetter season.

Of course, these patterns hit each region across the continent differently, said Dennis Hartmann, a professor of atmospheric sciences with the University of Washington.

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