Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Will Climate Change Temper El Niño’s Tantrums?

10.12.2002


The broad-scale warming expected from increased greenhouse gases may actually sap the strength of a typical El Niño, according to researchers at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. In contrast, the average El Niño during the last ice age may have packed more punch than today’s. The scientists have examined the past and future behavior of El Niño using a sophisticated computer model of global climate. They present their results this week at the annual meeting of the American Geophysical Union in San Francisco, December 6–10.


El Niño typically brings flooding to some parts of the world and drought to others. New research suggests El Niños have weakened since prehistoric times and could change still further in the future



More tepid El Niños to come?

NCAR scientist Esther Brady is lead author of a study that uses the NCAR Climate System Model to track how global air and ocean circulation could evolve at increasing levels of carbon dioxide, the most prevalent of the industrial greenhouse gases. The scientists simulated Earth’s climate with atmospheric carbon dioxide at one, two, and six times its preindustrial level of about 280 parts per million.


As greenhouse gases increase and global air temperatures rise, Brady’s results show a significant weakening of the average El Niño event. El Niño typically shifts warm water from the western Pacific toward the central and eastern tropics, as east-to-west trade winds weaken. Her simulations show an increase in cold upwelling off the coasts of Ecuador and Peru. This helps keep the eastern tropical Pacific from warming up as much as the west, sharpening the oceanic contrast that feeds the trade winds and helps keep El Niño at bay. Brady also found that greenhouse warming in the model led to a decoupling of the link between Pacific trade winds and the underlying sea-surface temperatures. This ocean-atmosphere link is believed to help drive the cycle of El Niño and its cool-water counterpart, La Niña.

Although this cycle might weaken on average in a greenhouse-warmed world, any given El Niño could still be intense, Brady notes. Even in the most extreme simulation, with six times the present-day level of carbon dioxide, large El Niños occur—but fewer overall.

Simulating El Niño’s past

It turns out there’s a history of diminished El Niño events in a warming world, according to another Climate System Model study. Led by NCAR’s Bette Otto-Bliesner, this project examined the period around 11,000 years ago, when global temperatures were rebounding from the last ice age. The average El Niño during this period in the computer simulation was about 20% weaker than today. The main factor responsible for the decrease is a slow shift in Earth’s asymmetric orbit around the Sun. Nowadays, Earth’s orbit comes closest to the Sun in early January, but 11,000 years ago, the closest approach came in the Northern Hemisphere summer, the season when most El Niños are just beginning to intensify. Along with other factors, the near-Sun approach may have provided enough extra heating to warm the western Pacific, while the eastern Pacific—where upwelling of cold water dominates—remained chilly. Driven by this intensified contrast, the east-to-west trade winds would strengthen, hindering developing El Niños.

Looking even further back in time, Otto-Bliesner and colleagues found that a more vigorous El Niño may have held sway when the last ice age was at its peak. Simulations for 21,000 years ago show the typical El Niño about 20% stronger than today. In the model, cold water sinks as it drifts from ice-covered southern oceans into the tropical Pacific. The thermocline—an oceanic boundary that separates surface warmth and subsurface chill—is thus strengthened, and the effect, says Otto-Bliesner, is to ramp up the average intensity of both El Niños and La Niñas.

Previous studies have differed on how intense El Niño events might have been in the past. She adds that both weak and strong El Niños show up in each era studied thus far, and more work is needed to arrive at a solid history. "The observational record is pretty short. El Niño may be changing already, but I don’t think we really know that yet."

Background: How El Niño works

A tight coupling between ocean and atmosphere produces the weather and climate impacts of El Niño and its counterpart, La Niña. During El Niño, the trade winds that usually blow from east to west across the tropical Pacific weaken, and the strong upwelling that normally keeps waters cool off Peru and Ecuador diminishes. This allows warmer water to extend across the tropical Pacific, rather than being confined to the west near Indonesia. Tropical showers and thunderstorms follow the warm waters eastward, toward South America. The air rising within these displaced storms helps steer upper-level winds and shape climate across much of the globe. In contrast, during La Niña, the trade winds strengthen, upwelling increases, and the eastern tropical Pacific is cooler than normal. This helps trigger a different set of climate impacts, some of them the opposite of those expected during El Niño. The entire system of ocean-atmosphere linkages is known as the El Niño–Southern Oscillation (ENSO).

Writer: Bob Henson

Bob Henson | EurekAlert!

More articles from Earth Sciences:

nachricht Upwards with the “bubble shuttle”: How sea floor microbes get involved with methane reduction in the water column
27.05.2020 | Leibniz-Institut für Ostseeforschung Warnemünde

nachricht An international team including scientists from MARUM discovered ongoing and future tropical diversity decline
26.05.2020 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Biotechnology: Triggered by light, a novel way to switch on an enzyme

In living cells, enzymes drive biochemical metabolic processes enabling reactions to take place efficiently. It is this very ability which allows them to be used as catalysts in biotechnology, for example to create chemical products such as pharmaceutics. Researchers now identified an enzyme that, when illuminated with blue light, becomes catalytically active and initiates a reaction that was previously unknown in enzymatics. The study was published in "Nature Communications".

Enzymes: they are the central drivers for biochemical metabolic processes in every living cell, enabling reactions to take place efficiently. It is this very...

Im Focus: New double-contrast technique picks up small tumors on MRI

Early detection of tumors is extremely important in treating cancer. A new technique developed by researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from normal tissue. The work is published May 25 in the journal Nature Nanotechnology.

researchers at the University of California, Davis offers a significant advance in using magnetic resonance imaging to pick out even very small tumors from...

Im Focus: I-call - When microimplants communicate with each other / Innovation driver digitization - "Smart Health“

Microelectronics as a key technology enables numerous innovations in the field of intelligent medical technology. The Fraunhofer Institute for Biomedical Engineering IBMT coordinates the BMBF cooperative project "I-call" realizing the first electronic system for ultrasound-based, safe and interference-resistant data transmission between implants in the human body.

When microelectronic systems are used for medical applications, they have to meet high requirements in terms of biocompatibility, reliability, energy...

Im Focus: When predictions of theoretical chemists become reality

Thomas Heine, Professor of Theoretical Chemistry at TU Dresden, together with his team, first predicted a topological 2D polymer in 2019. Only one year later, an international team led by Italian researchers was able to synthesize these materials and experimentally prove their topological properties. For the renowned journal Nature Materials, this was the occasion to invite Thomas Heine to a News and Views article, which was published this week. Under the title "Making 2D Topological Polymers a reality" Prof. Heine describes how his theory became a reality.

Ultrathin materials are extremely interesting as building blocks for next generation nano electronic devices, as it is much easier to make circuits and other...

Im Focus: Rolling into the deep

Scientists took a leukocyte as the blueprint and developed a microrobot that has the size, shape and moving capabilities of a white blood cell. Simulating a blood vessel in a laboratory setting, they succeeded in magnetically navigating the ball-shaped microroller through this dynamic and dense environment. The drug-delivery vehicle withstood the simulated blood flow, pushing the developments in targeted drug delivery a step further: inside the body, there is no better access route to all tissues and organs than the circulatory system. A robot that could actually travel through this finely woven web would revolutionize the minimally-invasive treatment of illnesses.

A team of scientists from the Max Planck Institute for Intelligent Systems (MPI-IS) in Stuttgart invented a tiny microrobot that resembles a white blood cell...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Dresden Nexus Conference 2020: Same Time, Virtual Format, Registration Opened

19.05.2020 | Event News

Aachen Machine Tool Colloquium AWK'21 will take place on June 10 and 11, 2021

07.04.2020 | Event News

International Coral Reef Symposium in Bremen Postponed by a Year

06.04.2020 | Event News

 
Latest News

Black nitrogen: Bayreuth researchers discover new high-pressure material and solve a puzzle of the periodic table

29.05.2020 | Materials Sciences

Argonne researchers create active material out of microscopic spinning particles

29.05.2020 | Materials Sciences

Smart windows that self-illuminate on rainy days

29.05.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>