El Nino... what is it? We know it happens in the Pacific Ocean between the west coast of South America and the east coast of Australia, and we know it is cyclical (every 4-7 years), but how can such a “little thing” impact the world’s weather? We hope this abbreviated section will give you an understanding of this phenomena!

Normally, trade winds blow across the Pacific from the Americas towards Austraila. As they do so, they push sun warmed surface water from east to west, creating what is referred to as “the warm pool” as it accumulates near Austrailia. Fine... this is normal.

But for some reason, the trade winds falter, and in some cases even reverses. As they do so, the warm water also reverses direction and sloshes eastward, back across the Pacific Ocean. Although no one knows for certain why this happens, it appears there may be some link between this reversal and sun spot activity. Regardless, this warm strip of water raises the sea level and sea temperature, stretching along the equator from the mid-Pacific to the coasts of Peru and Ecuador, influencing global patterns of winds and humidity.

And what does this do? Well for one thing, it diverts the course of the jet stream (a type of conveyor belt for storms), which in turn not only affects weather on the North American continent, but also over most of the world.

But that’s not the end of the story! El Nino can be modified by other events such as the “Pacific Decadal Oscillation” (PDO). The PDO is a subtle pattern of changing sea surface temperatures in the Pacific Ocean. The PDO itself is also cyclical, shifting between warm and cool phases every 20-30 years!

If El Nino begins during a cool phase of the PDO, El Nino tends to be milder and less predictable. On the other hand, El Ninos beginning during a warm PDO tend to be stronger and more predictable.

For more information on the Pacific Decadal Oscillation (PDO), click HERE

To return to the Natural Impacts Gateway page, click HERE

To return to the Climate Components Gateway page, click HERE

To return to the Climate Change Gateway page, click HERE

To return to the Issues Gateway page, click HERE

To return to the Impact Voters home page, click HERE

To leave a comment, click HERE

To join our EMail list, click HERE

Save Time!
To jump to the subject of interest to you, use our Quick Index by clicking HERE