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The University of Colorado-Boulder
5.9.24
Pedro DiNezio | University of Colorado Boulder
La Niña typically means cooler, wetter conditions on average globally, but not everywhere, and not every time. Luis Robayo/AFP via Getty Images
One of the big contributors to the record-breaking global temperatures over the past year – El Niño – is nearly gone, and its opposite, La Niña, is on the way.
Whether that’s a relief or not depends in part on where you live. Above-normal temperatures are still forecast across the U.S. in summer 2024. And if you live along the U.S. Atlantic or Gulf coasts, La Niña can contribute to the worst possible combination of climate conditions for fueling hurricanes.
Pedro DiNezio, an atmosphere and ocean scientist at the University of Colorado who studies El Niño and La Niña, explains why and what’s ahead.
“What is La Niña?
La Niña and El Niño are the two extremes of a recurring climate pattern that can affect weather around the world.
Forecasters know La Niña has arrived when temperatures in the eastern Pacific Ocean along the equator west of South America cool by at least half a degree Celsius (0.9 Fahrenheit) below normal. During El Niño, the same region warms instead.
Those temperature fluctuations might seem small, but they can affect the atmosphere in ways that ripple across the planet.
El Niño and La Niña Explained
How La Nina and El Nino form. NOAA.
The tropics have an atmospheric circulation pattern called the Walker Circulation, named after Sir Gilbert Walker, an English physicist in the early 20th century. The Walker Circulation is basically giant loops of air rising and descending in different parts of the tropics.
Normally, air rises over the Amazon and Indonesia because moisture from the tropical forests makes the air more buoyant there, and it comes down in East Africa and the eastern Pacific. During La Niña, those loops intensify, generating stormier conditions where they rise and drier conditions where they descend. During El Niño, ocean heat in the eastern Pacific instead shifts those loops, so the eastern Pacific gets stormier.
During La Niña, the Walker Circulation intensifies, triggering stronger storms where the air rises. Fiona Martin, NOAA Climate.gov
EL Niño and La Niña also affect the jet stream, a strong current of air that blows from west to east across the U.S. and other mid-latitude regions.
During El Niño, the jet stream tends to push storms toward the subtropics, making these typically dry areas wetter. Conversely, mid-latitude regions that normally would get the storms become drier because storms shift away.
This year, forecasters expect a fast transition to La Niña – likely by late summer. After a strong El Niño, like the world saw in late 2023 and early 2024, conditions tend to swing fairly quickly to La Niña. How long it will stick around is an open question. This cycle tends to swing from extreme to extreme every three to seven years on average, but while El Niños tend to be short-lived, La Niñas can last two years or longer.
La Niña and its opposite, El Niño
La Niña forms when surface temperatures in the tropical Pacific Ocean are about 0.5°C (0.9°F) below normal for three months. El Niño is the reverse, with temperatures warmer than normal. The chart shows the three-month rolling average temperature anomaly.
How does La Niña affect hurricanes?
Temperatures in the tropical Pacific also control wind shear over large parts of the Atlantic Ocean.
Wind shear is a difference in wind speeds at different heights or direction. Hurricanes have a harder time holding their column structure during strong wind shear because stronger winds higher up push the column apart.
La Niña produces less wind shear, removing a brake on hurricanes. That’s not good news for people living in hurricane-prone regions like Florida. In 2020, during the last La Niña, the Atlantic saw a record 30 tropical storms and 14 hurricanes, and 2021 had 21 tropical storms and seven hurricanes.
Forecasters are already warning that this year’s Atlantic storm season could rival 2021, due in large part to La Niña. The tropical Atlantic has also been exceptionally warm, with sea surface temperature-breaking records for over a year. That warmth affects the atmosphere, causing more atmospheric motion over the Atlantic, fueling hurricanes.
Does La Niña mean drought returns to the US Southwest?
The U.S. Southwest’s water supplies will probably be OK for the first year of La Niña because of all the rain over the past winter. But the second year tends to become problematic. A third year, as the region saw in 2022, can lead to severe water shortages.
Drier conditions also fuel more extreme fire seasons in the West, particularly in the fall, when the winds pick up.
During La Niña, the jet stream tends to be farther north, causing drier conditions across the U.S. Southwest. NOAA Climate.gov
What happens in the Southern Hemisphere during La Niña?
The impacts of El Niño and La Niña are almost a mirror image in the Southern Hemisphere.
Chile and Argentina tend to get drought during La Niña, while the same phase leads to more rain in the Amazon. Australia had severe flooding during the last La Niña. La Niña also favors the Indian monsoon, meaning above-average rainfall. The effects aren’t immediate, however. In South Asia, for example, the changes tend to show up a few months after La Niña has officially appeared.
La Niña is quite bad for eastern Africa, where vulnerable communities are already in a long-term drought.
Typical La Niña climate impacts, though conditions aren’t always like this. NOAA Climate.gov
Is climate change affecting La Niña’s impact?
El Niño and La Niña are now happening on top of the effects of global warming. That can exacerbate temperatures, as the world saw in 2023, and precipitation can go off the charts.
Since summer 2023, the world has had 10 straight months of record-breaking global temperatures. A lot of that warmth is coming from the oceans, which are still at record-high temperatures.
La Niña should cool things a bit, but greenhouse gas emissions that drive global warming are still rising in the background. So while fluctuations between El Niño and La Niña can cause short-term temperature swings, the overall trend is toward a warming world.”
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As the flagship university of the state of Colorado The University of Colorado-Boulder , was founded in 1876, five months before Colorado became a state. It is a dynamic community of scholars and learners situated on one of the most spectacular college campuses in the country, and is classified as an R1 University, meaning that it engages in a very high level of research activity. As one of 69 U.S. public institutions belonging to the prestigious Association of American Universities ), a selective group of major research universities in North America, – and the only member in the Rocky Mountain region – we have a proud tradition of academic excellence, with Nobel laureates and many members of prestigious academic academies.
University of Colorado-Boulder has blossomed in size and quality since we opened our doors in 1877 – attracting superb faculty, staff, and students and building strong programs in the sciences, engineering, business, law, arts, humanities, education, music, and many other disciplines.
Today, with our sights set on becoming the standard for the great comprehensive public research universities of the new century, we strive to serve the people of Colorado and to engage with the world through excellence in our teaching, research, creative work, and service.
The university is comprised of nine colleges and schools and offered over 150 academic programs and enrolled over 17,000 students. Nobel Laureates, MacArthur Fellows, and astronauts have been affiliated with CU Boulder as students, researchers, or faculty members. The university receives hundreds of millions of dollars for sponsored research to fund programs like the Laboratory for Atmospheric and Space Physics and JILA. CU Boulder has been called a Public Ivy, a group of publicly funded universities considered as providing a quality of education comparable to those of the Ivy League.
The Colorado Buffaloes compete in 17 varsity sports and are members of the NCAA Division I Pac-12 Conference. The Buffaloes have won national championships: in skiing, men’s and women’s cross country, and football. The university has produced Olympic medalists. Students participate in 34 intercollegiate club sports annually as well.
On March 14, 1876, the Colorado territorial legislature passed an amendment to the state constitution that provided money for the establishment of the University of Colorado in Boulder, the Colorado School of Mines in Golden, and the Colorado State University – College of Agricultural Sciences in Fort Collins.
Two cities competed for the site of the University of Colorado: Boulder and Cañon City. The consolation prize for the losing city was to be home of the new Colorado State Prison. Cañon City was at a disadvantage as it was already the home of the Colorado Territorial Prison. (There are now six prisons in the Cañon City area.)
The cornerstone of the building that became Old Main was laid on September 20, 1875. The doors of the university opened on September 5, 1877. At the time, there were few high schools in the state that could adequately prepare students for university work, so in addition to the University, a preparatory school was formed on campus. In the fall of 1877, the student body consisted of 15 students in the college proper and 50 students in the preparatory school. There were 38 men and 27 women, and their ages ranged from 12–23 years.
During World War II, Colorado was one of 131 colleges and universities nationally that took part in the V-12 Navy College Training Program which offered students a path to a navy commission.
University of Colorado-Boulder hired its first female professor, Mary Rippon, in 1878. It hired its first African-American professor, Charles H. Nilon, in 1956, and its first African-American librarian, Mildred Nilon, in 1962. Its first African American female graduate, Lucile Berkeley Buchanan, received her degree in 1918.
Research institutes
University of Colorado-Boulder’s research mission is supported by eleven research institutes within the university. Each research institute supports faculty from multiple academic departments, allowing institutes to conduct truly multidisciplinary research.
The Institute for Behavioral Genetics (IBG) is a research institute within the Graduate School dedicated to conducting and facilitating research on the genetic and environmental bases of individual differences in behavior. After its founding in 1967 IBG led the resurging interest in genetic influences on behavior. IBG was the first post-World War II research institute dedicated to research in behavioral genetics. IBG remains one of the top research facilities for research in behavioral genetics, including human behavioral genetics, psychiatric genetics, quantitative genetics, statistical genetics, and animal behavioral genetics.
The Institute of Cognitive Science (ICS) at CU Boulder promotes interdisciplinary research and training in cognitive science. ICS is highly interdisciplinary; its research focuses on education, language processing, emotion, and higher-level cognition using experimental methods. It is home to a state-of-the-art fMRI system used to collect neuroimaging data.
ATLAS Institute is a center for interdisciplinary research and academic study, where engineering, computer science and robotics are blended with design-oriented topics. Part of CU Boulder’s College of Engineering and Applied Science, the institute offers academic programs at the undergraduate, master’s and doctoral levels, and administers research labs, hacker and makerspaces, and a black box experimental performance studio. At the beginning of the 2018–2019 academic year, approximately 1,200 students were enrolled in ATLAS academic programs and the institute sponsored six research labs.
In addition to IBG, ICS and ATLAS, the university’s other institutes include Biofrontiers Institute, Cooperative Institute for Research in Environmental Sciences, Institute of Arctic & Alpine Research (INSTAAR), Institute of Behavioral Science (IBS), JILA, Laboratory for Atmospheric & Space Physics (LASP), Renewable & Sustainable Energy Institute (RASEI), and The University of Colorado Museum of Natural History
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