Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New findings show persistent El Niño-like conditions during past global warming

24.06.2005


During the most recent period in Earth’s past with a climate warmer than today, the tropical Pacific was in a stable state of El Niño-like conditions, according to a new study by researchers at the University of California, Santa Cruz.



Whether this represents a likely scenario for the future, given the current rise in global temperatures, is uncertain. Nevertheless, the study has important implications for scientists trying to understand the global climate system and how it might respond to global warming, the researchers said.

El Niño is a temporary disruption of normal circulation patterns in the ocean and atmosphere in the tropical Pacific, with important consequences for weather around the globe. Because the system always returns to the normal circulation patterns after an El Niño event, many scientists have considered these patterns to be the only state in which the system can remain stable over long periods of time. The new study, published this week in the journal Science, shows that there is another stable state for the ocean-atmosphere system that is dramatically different from today’s.


"The stable configuration that we’ve gotten used to is not the only stable configuration for the tropical Pacific, and this suggests that the Earth’s system for global heat transport functioned in a fundamentally different way the last time the climate was warmer than it is today," said the study’s lead author, Michael Wara.

Wara, who earned a Ph.D. in ocean sciences at UCSC, is now studying law and environmental policy at Stanford University. His coauthors are Christina Ravelo, associate professor of ocean sciences at UCSC, and Margaret Delaney, professor of ocean sciences at UCSC.

The researchers based their findings on an analysis of hundreds of samples from sediment cores drilled from the ocean floor on opposite sides of the tropical Pacific Ocean. The sediment cores were obtained by the international Ocean Drilling Program from a site near Indonesia in the western Pacific and another site near the Galapagos Islands in the eastern Pacific.

The sediments contain the microscopic shells of tiny sea creatures called foraminifera that lived in the surface waters of the ocean. The chemistry of these shells--in particular, the ratio of magnesium to calcium--is highly sensitive to the temperature of the water in which they formed. By analyzing the composition of the shells, the researchers were to reconstruct a detailed record of sea-surface temperatures in the tropical Pacific during the Pliocene epoch, which lasted from about 5 million years ago to about 1.7 million years ago.

Currently, the normal sea-surface temperatures in the tropical Pacific show a strong gradient from cool temperatures in the eastern Pacific off South America, where upwelling of cold deep water occurs, to much warmer temperatures in the west, where the trade winds pile up warm surface waters. During an El Niño, the trade winds slacken and warm water spreads eastward across the tropical Pacific, drastically weakening the temperature gradient. The UCSC researchers found that sea-surface temperatures during the Pliocene were much like those seen during an El Niño event.

"It looks like a permanent El Niño," Ravelo said. "We know El Niños have far-reaching global climate effects today, so that gives us an idea of what the global climate system may have been like during the Pliocene."

The UCSC group’s findings contradict a study published earlier this year in Science, which used the same methods but found cooler rather than warmer temperatures in the eastern Pacific. Ravelo said the difference is probably due to the much smaller number of samples analyzed in the earlier study. The UCSC group obtained more than 400 data points for the same time period covered by six data points in the earlier paper.

"Maybe they were unlucky and got a couple of samples that don’t represent that time period well," Ravelo said.

Previous research by Ravelo and others has shown that conditions outside the tropics during the Pliocene were also consistent with a permanent El Niño-like state. The global consequences of El Niño events include dramatic changes in rainfall patterns, causing serious flooding in some areas while other regions experience droughts. Shifts in ocean temperatures also spread beyond the tropics, affecting fisheries along the California coast, for example.

According to Ravelo, however, the El Niño-like conditions of the Pliocene should not be regarded as a direct analogy for the future effects of global warming. Rather, the Pliocene climate should serve as a target for global climate models to test their ability to reproduce the full range of possible climate states. Climate experts use computer-driven climate models to help them understand how the climate system works and how it is likely to respond to changes such as the increasing concentration of greenhouse gases in the atmosphere.

"The current climate models are very good at reproducing stable conditions in the tropics like we have today, but they should also be able to reproduce this very different tropical climate state that was stable in the past. If they can’t, we know there is something missing," Ravelo said.

The new study reinforces the notion that the coupled systems of oceanic and atmospheric circulation that drive the global climate are capable of dramatic shifts from one stable state to another.

"Many aspects of the climate system that appear stable within a certain range of temperatures can shift dramatically when a particular threshold is passed," Wara said. "We can’t say where that threshold is, but it is a concern as we continue this ongoing global experiment of adding greenhouse gases to the atmosphere."

Tim Stephens | EurekAlert!
Further information:
http://www.ucsc.edu

More articles from Ecology, The Environment and Conservation:

nachricht How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>