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 How much biomass grows in the savannah?
16.02.2017 | Friedrich-Schiller-Universität Jena

nachricht Canadian glaciers now major contributor to sea level change, UCI study shows
15.02.2017 | University of California - Irvine

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Biocompatible 3-D tracking system has potential to improve robot-assisted surgery

17.02.2017 | Medical Engineering

Real-time MRI analysis powered by supercomputers

17.02.2017 | Medical Engineering

Antibiotic effective against drug-resistant bacteria in pediatric skin infections

17.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>