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

More articles from Earth Sciences:

nachricht Water - as the underlying driver of the Earth’s carbon cycle
17.01.2017 | Max-Planck-Institut für Biogeochemie

nachricht Modeling magma to find copper
13.01.2017 | Université de Genève

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Global threat to primates concerns us all

19.01.2017 | Ecology, The Environment and Conservation

Scientist from Kiel University coordinates Million Euros Project in Inflammation Research

19.01.2017 | Awards Funding

The Great Unknown: Risk-Taking Behavior in Adolescents

19.01.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>