UNIVERSITY OF BERN
Bern’s ice core researchers were already able to demonstrate in 2008 how the concentration of CO2 in the atmosphere has changed over the past 800,000 years. Now, using the same ice core from the Antarctic, the group led by Bernese climate researcher Hubertus Fischer shows the maximum and minimum values between which the mean ocean temperature has fluctuated over the past 700,000 years. The results of the reconstruction have just been published in the journal Climate of the Past.
The study’s key findings: Mean ocean temperatures have been very similar over the last seven ice ages, averaging about 3.3 °C colder than the pre-industrial reference period, as already suggested by syntheses of deep water temperatures from marine sediments. However, ocean temperatures in the warm periods 450,000 years ago were much colder and CO2 concentrations were lower than in our present warm period, despite similar solar radiation. The new measurements show that ocean temperature is also shaped by changes in ocean circulation. The so-called global circulation of deep waters has a significant impact on heat storage in the ocean.
“To understand how the climate system’s heat balance is changing,” says Hubertus Fischer, “we have to understand the ocean first and foremost.” For example, 93 percent of the additional heat that humans accumulate by increasing greenhouse gases is currently stored in the ocean rather than in the atmosphere. This means that without the ocean’s heat uptake, the temperature increase measured on land due to human-induced climate change would be significantly greater. However, because the oceans have a huge mass compared to the atmosphere, the temperature changes measured in the ocean today are very small. Measurements on a few ice samples are sufficient
The relevance of data from the ocean for climate research is demonstrated by the international ARGO project, a mobile observation system for the world’s oceans with which for example continuous temperature measurements down to a depth of 2,000 meters have been carried out since 2000. Roughly 4,000 drifting buoys distributed over all oceans are used for this. This makes the approach of Bern’s researchers all the more astonishing in comparison: “We only need a single polar ice sample for our mean ocean temperature measurement,” explains Hubertus Fischer, “of course we are nowhere near the accuracy of ARGO, but conversely we can look far back into the past.” What is being studied is not frozen seawater, but air bubbles trapped in Antarctica’s glacier ice. Specifically: the noble gases argon, krypton, xenon and molecular nitrogen. The majority of these gases are in the atmosphere, just a small fraction is dissolved in the ocean. How well each gas is dissolved in seawater depends on the ocean temperature. Therefore, the changing ratio of these gases in the ice samples can be used to reconstruct past mean ocean temperatures.High-precision gas measurements by Bernese researchers
“The prerequisite for this method are high-precision measurements using a dynamic mass spectrometer,” emphasizes Hubertus Fischer, “which were made possible by the great efforts of several doctoral students and postdocs involved in the publication.” Processing and measurement methods developed in Bern as part of the MATRICs project funded by the European Research Council (ERC) are also crucial. Past ocean temperatures are determined to within 0.4 °C in Bern. This precision makes it possible to trace the climatic ups and downs of the past, since the difference in mean ocean temperature between the ice age and the warm phases over the past 700,000 years was about 3 °C. In addition to the laboratory in Bern, only the Scripps Institute of Oceanography in San Diego, USA, which Bern’s researchers work closely with, has so far carried out such measurements worldwide.
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Too bad they didn’t name the journal: “Climate: Changing the Past for a Better Future”.
From the above article’s last paragraph:
“Past ocean temperatures are determined to within 0.4 °C in Bern. This precision makes it possible . . . “
Actually, the claimed precision is obviously not based on any direct measurement of “past ocean temperatures”, but instead is based on inferring temperature from asserted-to-be “precise” measurements of one or more ocean temperature PROXIES. Now what could go wrong with that? . . . thinking about tree rings as a proxy? . . .
Also this from the second-to-last paragraph of the above article:
“How well each gas is dissolved in seawater depends on the ocean temperature.”
But gas solubility in seawater also depends on other significant variables, such as salinity, gas partial pressure above the water surface, diffusion through floating surface ice if present, diffusion/convection through subsurface concentration gradients which in turn are affected by ocean currents or lack thereof, etc.
Combine these issues the Bern researchers’ claim they can derive global mean ocean temperatures just using a few ice cores from Antarctica, when in fact nobody can accurately state how global ocean circulation patterns have varied over the last 700,000 years. Really?
Sorry, but the above article is just not scientifically credible.
“For example, 93 percent of the additional heat that humans accumulate by increasing greenhouse gases is currently stored in the ocean rather than in the atmosphere.”
93% of nothing is nothing, so this is not even wrong.
I believe using ratios of noble gases and molecular nitrogen trapped in ice cores
is a valid scientific method to determine long-term, historic oceanic temperatures.
So, in criticizing the recent remarks of the researcher from the University of Bern
with regards to “carbon dioxide/methane greenhouse warming” in the atmosphere
magically relating to those ratios of molecules/isotopes trapped in ice cores — and
to the oceanic temperatures they indicate (assertions studiously emphasized in the
original research paper) — we must not throw out the baby with the bathwater.
I believe in the conclusion of those researchers that a very large fraction of any
excess heat that might have entered the Earth (of course, from the Sun) in the past,
raising its overall temperature, has been sequestered in the oceans and only a very
small amount has manifested itself in the atmosphere and on the land surface of the
Earth. After all, about 70% of all sunlight falls on water in the first place when it
reaches Earth’s surface. And water has a thermal capacity of about 700 times air. And if the heat absorption mechanism operating here involves mainly the oceans and NOT the atmosphere, that would clinch the conclusion. Notice that this conclusion is entirely separate from the glib remarks of one of those Bern researchers that this extra thermal energy is coming from “increasing greenhouse gases”, which, to put it mildly, is mind-blowing, junk science (though it will earn him Liberaloid brownie points). How can a hot atmosphere efficiently conduct its heat, through infrared radiation, over a matter of a few hundred years, downwards into the oceans so that they eventually retain 93% of that heat?
This overriding sequestration of thermal energy in the oceans is what can cause,
over time, vast amounts of floating ice (shelves or otherwise) in the vicinity of the
poles to melt, sometimes endangering the sheet ice they were protecting from meeting the same fate. And this is what can cause, over time, ocean levels to rise (through thermal expansion or net sheet ice melting overcoming snow accumulation). And it can add a lot of noise to average global (surface) temperature graphs plotted against time, as vertical ocean currents can bring up or take down vast amounts of heat from and into the depths of the ocean over 10-year time frames. In other words, global climate researchers should be thinking a lot more about the oceans than the atmosphere.
Those Bern researchers are also maintaining that in the present interglacial the
oceans are anomalously warmer than in the past 6 ones, which is a very intriguing
insight (which I also believe is true, though controversial).
Thus, this is very important research, unfortunately, marred by numerous,
gratuitous, politicized remarks thrown in by the research leader as an afterthought.
I would really like to see the error analysis for this project. The quantity of assumptions which are required to assume that their precise measurements of ice core gas bubbles accurately represents the concentration of gases in the air from 700 centuries before the present is truly mind numbing.
Looking at the ice core laid horizontally, it could be a 700,000-year handle- using a “nature-trick,” we could graft modern temp records onto it, as a blade (going up, very scary), and we’d have evidence of AGW. Simples.