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 Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

A new technique isolates neuronal activity during memory consolidation

22.06.2017 | Life Sciences

Plant inspiration could lead to flexible electronics

22.06.2017 | Materials Sciences

A rhodium-based catalyst for making organosilicon using less precious metal

22.06.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>