I live in the Midwestern US, for context.
I understand that La Niña and El Niño are more or less cyclical (ignoring ENSO Neutral which just seems to more often than not just be a transition between the two) and that weather effects differ depending on where you are in the world. But it seems as if every time there’s a transition between the two, no matter if we’re transitioning to La Niña or El Niño, it somehow means that we’re “really in for a hot one this year!”
[A 2024 article from CNN explaining that La Niña makes it hot](https://www.cnn.com/2024/06/13/weather/el-nino-la-nina-summer-forecast-climate/index.html).
[A 2020 article, also from CNN, indicating that El Niño leads to higher world average temperatures](https://amp.cnn.com/cnn/2020/09/10/weather/la-nia-is-here-trnd)
Surely they can’t both mean hotter than normal, right? We’re almost always in one or the other. If it’s hotter than average all the time, then that’s the new average.
Make it make sense.
In: Planetary Science
ENSO is an acronym for El Niño and the Southern Oscillation.
Under normal atmospheric conditions, wind blows from east to west along the equator. This pushes warm surface water ahead of it to the western Pacific. That water is replaced with colder water from below. Larger current patterns also contribute to the eastern margins of the pacific being relatively cold.
During an El Niño event, those winds are lighter than normal or break down all together. The reduced wind pressure allows the warm surface water to slosh back to the eastern Pacific. Since this happens around late December (or is noticed then) it’s called El Niño or the Christ Child. The warmer water fuels more energy and moisture in the atmosphere, bringing warmer and typically wetter than average winters to the regions.
I’m not familiar with what happens east of the Rockies.
In the western Pacific, the water is colder than average and results in lower atmospheric moisture. This is the Southern Oscillation. Lower moisture and temperature is frequently associated with a breakdown of monsoons in Asia. Lower moisture also results in drought in Australia.
La Niña is the name given to periods with greater equatorial winds and greater upwelling of cold water. This results in lower moisture and rain events in the eastern pacific and warmer temperatures and greater moisture in the Western. The eastern Pacific may expect drought which contributes to other effects (lower transpiration can affect local temperatures) but the basic oscillation says when it’s hot one side it’s cold in the other side.
There’s a lot of complexity around global warming and other factors, but that’s the gist as taught in my college climate courses.
El Niño means the Pacific Ocean is hotter than usual
La Niña means the Pacific Ocean is cooler than usual
The Pacifc Ocean doesn’t greatly affect you, being in the Midwest, nor me, being in the Northeast. We have the Great Lakes affecting our weather, and I also have the Atlantic.
El Niño means hot temperatures for the West Coast (because hot water means hot air)
La Niña means less rainfall for the Pacific Northwest (because less water is evaporated from the ocean) which naturally makes it warmer, since there’s no rain to cool things down. This generally leads to cooler temperatures on the West Coast, but it doesn’t have to.
Are we getting more hurricanes or not this year on the East coast?
Effects are pretty different for different parts of the world. Some places get hotter and wetter during El Niño and some places get colder and dryer.
El Niño/La Niña has a better relationship to wetter/drier more so than hotter/colder.
The temperature of the Pacific Ocean off the coast of South America (where we determine El Niño vs La Niña) influences the track storms take both across the U.S. and in the Gulf of Mexico (Hurricane season).
Regardless of which one we are in, the amount of green house gases in the atmosphere continues to rise, trapping more heat and that’s why we continually set monthly heat records.
Because baseline is hotter than normal. In fact they move the historical averages up 10 years once every ten years, so now normal is hotter than normal
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