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The Phenomenon of El Niño and La Niña

Get ready for another wet winter…this doesn’t sound like a normal statement here in Southern California. However, in a recent analysis from NASA’s sea level change scientists, a strong El Niño this winter could bring intense rainstorms and extra floods that can impact low sea-level cities and coastal neighborhoods. Residents from the West Coast are still hearing of the major drought that has plagued Southern California for the last two decades. Now, the last few winters have brought more rain than usual and have eased the drought a bit, but could climate change affect the coming rainstorms in California, and subsequently, affect the weather phenomenon that is “El Niño”?

What is “El Niño” and “La Niña”?

To explain what El Niño is, we would also have to explain the accompanying weather phenomenon of La Niña. If you have lived on the West Coast of the US, close enough to the Pacific Ocean, you may have heard the term El Niño or La Niña come up every so often during our Winter and sometimes into our Spring months. According to NASA, El Niño, translated from “little boy” from Spanish, is characterized by “higher-than- normal sea levels and warmer-than-average ocean temperatures along the equatorial Pacific.” The weather phenomenon usually happens between the months of January through March, but can last for many months after that. Furthermore, an El Niño and La Niña event occurs on average anywhere between two and seven years but there is no true regular schedule. El Niños generally happen more often than La Niñas, according to the National Oceanic and Atmospheric Administration (NOAA). However, California and the West Coast just bid farewell to La Niña a few short months ago. La Niña is translated as “little girl” in Spanish, and is known for having the opposite effect of El Niño. Sometimes known as simply “a cold event,” La Niñas will bring “persistent colder-than-normal sea surface temperatures across the central and eastern Pacific”. Warmer water will push further west than usual, causing our U.S. Western Coasts to deal with the colder fronts.

What happens during El Niño and La Niña?

The map above illustrates the jet stream track changes during El Niño. Credit: NOAA

During El Niño, warm water from the Pacific Ocean is pushed east towards the western coast of the United States (California, Oregon, and Washington). According to NOAA, the warmer waters cause the Pacific jet stream - which is a narrow band of strong winds above the Pacific Ocean - to move further south and east of its normal position. This affects our weather, especially during winter, as it leads to wetter conditions than usual in the Southern U.S. and warmer and drier conditions in the North. Upwellings in the ocean occur when winds push surface water away from shores and deeper water rises in its place. Normal oceanic conditions have upwellings that bring cold and nutrient-rich water from the depths to the surface and shoreline. However, in El Niño, upwelling weakens or stops altogether. This also greatly impacts our marine life. Without the nutrients from the deep, a chain reaction happens: there are fewer phytoplankton off the coast, affecting the fish that eat phytoplankton and, in turn, affecting everything that eats fish. 

La Niña causes the jet stream to move northward and weaken over the eastern Pacific, bringing warmer and drier winters to the South and wetter, colder winters to the North. Credit: NOAA

As mentioned before, the opposite effect of El Niño tends to happen during La Niña. In the case of La Niña, trade winds are stronger than usual and will push warm water west towards Asia, away from the eastern end of the Pacific where California sits. With colder water more present with these conditions, upwelling increases and brings more cold nutrient-rich water to west coast surfaces. With more nutrients in the water, more of the marine environment is supported and cold-water species like squid and salmon are brought to the California coast. While marine life off the west coast thrives with the nutrient-rich water, La Niña events also affect the temperatures inland from changes in the jet stream. Cold water of the Pacific pushes the Polar Jet Stream to the north, bringing colder and wetter winters to the Northern U.S. and Canada. As the Polar Jet Stream moves north, the South is exposed to drier and warmer winters- this has been the case for Southern California’s drought over the last several years.


How Can Climate Change Affect El Niño And Our Weather?

An increase in greenhouse gas emissions may also increase the frequency of when El Niños and La Niñas occur, according to Michael Phaden, the senior scientist at NOAA’s Pacific Marine Environmental Laboratory. While the exact projection of how much rainfall we could see here in the Western U.S. is less clear, more extreme storms brought by El Niño are growing in likelihood with our warming climate. In a recent scientific article, Phaden demonstrated that El Niño and La Niña events have most likely, “increased in amplitude by up to 10% since 1960.” While 10% may not sound like a lot, the article goes on to say that any increase in range on our strongest weather events only amplifies the floods, rainstorms, and heat waves that an El Niño season already brings. 

Huntington Beach, Jan 05 2023. Mark Rightmire/MediaNews Group/Orange County Register Via Getty

Goodbye La Nina

The cycle of warm El Niño and cold La Niña events that happen in the Pacific Ocean is known as El Niño Southern Oscillation, or ENSO. As one of the most dramatic yearly variations of Earth’s weather that occur every few years, ENSO events can affect our agriculture, public health, freshwater availability, and economic activity around the world. Southern California began experiencing an increase in dry winters from a La Niña event that began in September of 2020 and continued into 2021 and 2022. However, the National Oceanic and Atmospheric Administration announced in March of 2023 that the event of La Niña from September 2020 had ended. As La Niña ended, the prediction for Southern California weather in 2023 was to expect less hot and dry conditions, and less likelihood of drought and wildfire. With 2023 coming to a close, California saw surprisingly below-normal temperatures from low-pressure systems over the summer. Western Regional Climate Center researcher Dan McEvoy said, although some daily temperatures were still broken in July throughout some California cities, the state overall experienced one of its coolest summers since 2011. The ending of La Niña in early 2023 could be one factor in this cooler summer, however, climatologists are still pointing out that our overall global temperatures are still rising- possibly affecting how we will see the development of El Niño this year.


As we enter El Niño season…  

We might continue hearing the buzz about potentially strong El Niño effects, but like any other strong weather, it is important to properly prepare in the event of an intense rainstorm and be on the lookout for any weather warnings released in your area. Hearing the news of global warming and what it affects in our daily lives is difficult to process, as it can feel overwhelming. However, it is important to see that such news can serve as a reminder that the fight to protect our world is far from over. There are many studies that still need to be conducted and much data that still needs to be collected to reach an official conclusion on the impact of global warming on weather phenomena like El Niño and La Niña. With the extensive number of studies illustrating the projected impact of global warming, we know how imperative it is to limit our emissions of greenhouse gases around the world. You can do your part by educating yourself about the environment (you are already doing it!), voting with your dollar when purchasing small or large consumables, volunteering with local conservation and climate action nonprofits, and using your voice by writing letters to local, state and federal representatives about your desire for a safer and healthier planet.


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