Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How variable are ocean temperatures?

11.11.2014

New study shows significant differences between climate archives and climate models

The earth’s climate appears to have been more variable over the past 7,000 years than often thought. This is the conclusion of a new study forthcoming online this week in the U.S. scientific journal “Proceedings of the National Academy of Sciences” (PNAS). In the study, scientists from the Potsdam-based Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, and Harvard University show that sea surface temperatures reconstructed from climate archives vary to a much greater extent on long time scales than simulated by climate models. The consequence: either the analysed climate archives supply inaccurate temperature signals, or the tested models underestimate the regional climate fluctuations in the Earth’s recent history.


BU: Scientists analysing a sediment core.

Photo: Thomas Ronge, Alfred-Wegener-Institut

In order to reconstruct climate history, it is necessary to study natural climate archives since, in terms of the Earth’s history, humankind has only very recently begun measuring the planet. There have been instrumental measurements of ocean temperatures for only around 150 years now. For periods prior to that, scientists have to rely on “proxies”, i.e. indicators enabling indirect conclusions to be drawn about climate data from earlier times. Such climate archives generally refer to spatially limited areas and differ in their temporal resolution. They may also include significant “background noise”.

“In our study we weren’t interested in how warm the climate might have been at time X in a specific region. We wanted to retrospectively analyse how much the regional climate temporally varies over decades to millennia,” explains Dr. Thomas Laepple from the Alfred Wegener Institute. “One of our biggest challenges was to make it possible to compare various measured data and climate archives from a wide variety of regions and filter out the natural noise that can greatly distort the signal of climate archives.”

Laepple and his colleague Peter Huybers from Harvard University compared data from temperature measurements, corals and sediment cores originating from many different marine regions of the world. Climate data from modern corals date back no more than 400 years. They allow conclusions to be made about temperature changes over decades or centuries. Marine sediments may contain much older data, but generally only achieve a centennial or millennial resolution. Using different calibration and filtering processes, the two researchers succeeded in combining a wide variety of available data from temperature measurements and climate archives in such a way that they were able to compare the reconstructed sea surface temperature variations at different locations around the globe on different time scales over a period of 7,000 years.

“We initially determined that the natural variations of ocean temperatures are surprisingly large – and the longer the periods we analysed, the greater the variations,” was the initial conclusion of the two scientists. Then, in a second step, they studied around 20 climate models in over 100 test runs to ascertain how well the models can simulate these temperature variations. The result: measured and climate archive data closely correspond to model runs for periods of years. Toward longer timescales, however, discrepancies grow – most significantly in tropical marine regions. On a millennial time scale, conventional climate models underestimated the variations of sea surface temperatures reconstructed from climate archives by a factor of 50.

“Fundamentally, there are only two explanations,” says Thomas Laepple. “Either the climate archives do not provide reliable temperature data, or the climate models underestimate the variability of the climate. Or both may be true to some extent.” The results are based on a number of independent climate archives, as well as instrumental records, and hold up whilst applying a wide range of correction methods, which leads Laepple to believe that the problem lies more with the models.

“We seem to have to revise upward predictions of how much climate can regionally vary,” suggests Thomas Laepple, based on his findings. “Given the huge amount of greenhouse gases released into the atmosphere, we can be sure that it is getting warmer globally. But the range of changes we are headed for could well be larger than we have generally expected.” This has to do with the fact that the natural variations in combination with the warming trend always point in both directions: over a period of decades or a hundred years temperatures in a particular region may rise to a lesser or greater degree than present-day climate models generally forecast.

Since this is a central issue for the forecasting of future climatic conditions on the Earth, for about a year now the physicist in Potsdam has been heading an interdisciplinary research group that focuses specifically on this topic. It is called “ECUS – Estimating climate variability by quantifying proxy uncertainty and synthesizing information across archives”.

According to Laepple: “We are in the middle of an experiment that we cannot reverse, but which we still don’t understand well enough to make clear statements at the regional level on longer time scales. Unfortunately, we will just have to continue to live with this uncertainty for some time.”

Information for journalists:

The study will be published in the week starting November 10, 2014 in the online early edition of the Proceedings of the National Academy of Sciences (PNAS).

Authors and title: Thomas Laepple und Peter Huybers: Ocean surface temperature variability: Large model–data differences at decadal and longer periods. DOI: 10.1073/pnas.1412077111 (Link: www.pnas.org/cgi/doi/10.1073/pnas.1412077111  or in the online early edition unter http://www.pnas.org/content/early/recent )

Your scientific contact person at the Alfred Wegener Institute is Dr. Thomas Laepple (phone: +49-177-2398233, email: Thomas.Laepple@awi.de). Your scientific contact person at Harvard University is Prof. Dr. Peter Huybers (phone: +1-617-495-4811; email: phuybers@fas.harvard.edu).

Your contact person in the AWI press department is Ralf Roechert (phone: +49-471-4831-1680; email: medien@awi.de).

Follow the Alfred Wegener Institute on Twitter and Facebook. In this way you will receive all current news as well as information on brief everyday stories about life at the institute.
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and in the high and mid-latitude oceans. The Institute coordinates German polar research and provides important infrastructure such as the research ice breaker Polarstern and research stations in the Arctic and Antarctic to the national and international scientific world. The Alfred Wegener Institute is one of the 18 research centers of the Helmholtz Association, the largest scientific organisation in Germany.

Folke Mehrtens | idw - Informationsdienst Wissenschaft
Further information:
http://www.awi.de

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>