The Eemian is a poor analogue for current climate change
12.06.2012/Kiel. The Eemian interglacial period that began some 125,000 years ago is often used as a model for contemporary climate change. In the international journal “Geophysical Research Letters” scientists from Mainz, Kiel and Potsdam (Germany) now present evidence that the Eemian differed in essential details from modern climatic conditions.
To address the question about how climate may develop in the future, earth scientists direct their attention to the past. They look for epochs with similar conditions to today. The major identified climatic processes are then simulated with numerical models to further test possible reactions of the Earths’ system.
An epoch which is often regarded suitable for such an undertaking is the Eemian warm period, which began around 125,000 years ago following the Saalian ice age. For about 10,000 years, average temperatures on Earth in the Eemian were rather enhanced – probably several degrees above today’s level. This seems to be well documented in both ice cores as well as terrestrial records from land vegetation. Substantial parts of the Greenland ice had melted, and global sea level was higher than today. “Therefore, the Eemian time is suited apparently so well as a basis for the topical issue of climate change”, says Dr Henning Bauch, who works for the Academy of the Sciences and the Literature Mainz (AdW Mainz) at GEOMAR | Helmholtz Centre for Ocean Research Kiel.
However, in a study which appears in the recent issue of the international journal “Geophysical Research Letters” Dr Bauch, Dr Evgeniya Kandiano of GEOMAR as well as Dr Jan Helmke of the Institute for Advanced Sustainability Studies in Potsdam now show that the Eemian warm period differed from the present day situation in one critical aspect – the development in the Arctic Ocean.
In our current warm period, also called Holocene, oceanic and atmospheric circulation delivers large amounts of heat northward into the high latitudes. The most well known heat conveyer is the Gulf Stream and its northern prolongation called the North Atlantic Drift. The currents provide not only the pleasant temperatures in Northern Europe, they also reach as far as the Arctic. Studies in the last years have shown that the oceanic heat transport to the Arctic has even increased, while the summer sea ice cover in the Arctic Ocean seems to be decreasing continuously. It has long been assumed that such conditions also prevailed 125,000 years ago. Accordingly, the Arctic should have been by and large ice-free in the Eemian summers.
Dr Bauch’s group examined sediment cores from the seabed in which information about the climate history of the past 500,000 years is stored. These come from the Atlantic to the west of Ireland and from the central Nordic Seas to the east of the island of Jan Mayen. The sediments contain minute calcite tests of dead microorganisms (foraminifers). “The type of species assemblage in the respective layers as well as the isotopic composition of the calcitic tests give us information about temperature and other properties of the water in which they lived at that time“, explains Dr Bauch.
The samples from the Atlantic delivered the higher-than-Holocene temperature signals so typical for the Eemian. The tests from the Nordic Seas, however, tell quite another story. “The found foraminifers of Eemian time indicate comparatively cold conditions”. The isotope investigations of the tests, in combination with previous studies of the group, “indicate major contrasts between the ocean surfaces of these two regions “, according to Dr Bauch. “Obviously, the warm Atlantic surface current was weaker in the high latitude during the Eemian than today.” His explanation: “The Saalian glaciation which preceded the Eemian was of much bigger extent in Northern Europe than during the Weichselian, the ice age period before our present warm interval. Therefore, more fresh water from the melting Saalian ice sheets poured into the Nordic Seas, and for a longer period of time. This situation had three consequences: The oceanic circulation in the north was reduced, and winter sea ice was more likely to form because of lower salinity. At the same time, this situation led to a kind of ‘overheating’ in the North Atlantic due to a continuing transfer of ocean heat from the south.”
On the one hand, the study introduces new views on the Eemian climate. On the other hand, the new results have consequences for climatology in general: “Obviously, some decisive processes in the Eemian ran off differently, like the transfer of ocean warmth towards the Arctic. Models should take this into consideration if they want to forecast the future climate development on the basis of past analogues like the Eemian “, says Dr Bauch.
Reference:
Bauch, H. A., E. S. Kandiano, J. P. Helmke (2012): Contrasting ocean changes between the subpolar and polar North Atlantic during the past 135 ka. Geophysical Research Letters, 39, 2012, http://dx.doi.org/10.1029/2012GL051800
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Source: Joint press release of the Academy of the Sciences and the Literature Mainz and the GEOMAR | Helmholtz Centre for Ocean Research Kiel.
UPDATE: A copy of the paper is available here (Thanks to Dr. Leif Svalgaard)
vukcevic says:
June 15, 2012 at 1:16 pm
Hit it with a strong magnetic storm, Antarctica will follow…
To see why this is dead wrong you need only consider the concept of skin-depth. This is the distance an external disturbance will travel into a medium. The skin depth depends on the conductivity of the medium and the frequency of the disturbance variation. For periods around one day [typical for a geomagnetic storm] the lower mantle has a skin depth of about 50 km, while the outer core has a skin depth of only 200 meter. So it is impossible for geomagnetic storms to penetrate into the core and change anything.
The prevailing dogma is that the north atlantic drift maintains climate warmth and – as per “Day after tomorrow”, cut off of this current spells catastrphic freezing.
This research shows the Eemian to contradict this picture – a world without the NAD has a colder Arctic but is warmer overall. Interesting stuff. Scientific dogmas often become like glass houses and real experimental data can behave like flying pieces of masonry…
@ur momisugly Johnputs: … and the name of your religion is …
johnpnts says:
June 15, 2012 at 5:36 pm
Humans have evolved on this planet and have surpassed the natural world. We are responsible for filling every corner of the land. …….. . Energy and the possession of natural resources that we know are detrimental to life, such as oil, coal, gas, and uranium all pollute the earth, warm the atmosphere, and have nearly sealed our fate.
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So please go find a cave to live in and leave the rest of us alone.
PS Hansen says CO2 is detrimental to life. Do you breath?
Take a deep breath and think about it.
johnpnts has challenges in his life, as mentioned on 16th January 2012 in his “Free Energy Now” website. As energy can be neither created nor destroyed, I suspect what he really wants is free fuel. It’s all a bit sad.
http://johnpnts.wordpress.com/
Better to be thought a fool than to disclose one’s beliefs and confirm opinion.
@johnpnts:
John, you no doubt will recognize the following quote:
“…….. all I have that is non-material: the love of my kids and wife, living in the country on my families 125 year-old farm, having the right to own land, and the freedoms that are theoretically accorded to us in this country, I am truly grateful. ”
I now have a question for you: Please name one country or epoch where the above can be true and there is NO imbalance in wealth. Good Luck.
Leif Svalgaard says: June 15, 2012 at 8:23 pm
……..
I know all of that, could be ‘geomagnetic storm’ as in http://www.vukcevic.talktalk.net/LFC2.htm but we don’t want to go there. From the Andy Jackson’s data it can be calculated that the strongest spectral component is at exactly 21.28 years (its timing is curiously about 7 years after the even number SC max) , second strongest component is found in the Arctic only, and it doesn’t appear to be harmonic/sub-harmonic of the solar output, so I concluded it has to be a local resonance associated with effect of two NH’s poles. I will write a bit more about what I found in the data, and then you can have another go at it.
The reverse would appear to be also true as during an ice age the Arctic is warmer. Settlements of surprisingly large populations in the arctic from the time of the last ice age, and the transit of people into North America would support the fact.
.”A warmer earth necessarily warms 3-5 times more at the poles than the equator due to the efficiency of heat transport. It is not primarily the ocean but the atmosphere that transports the heat poleward.”
Evidence please ?
So far as I have seen, the poles get colder when the Earth gets warmer save that in the Arctic warmth gets into the Arctic Ocean via water flowing in from the north Atlantic.
The greatest warming would be on the equatorial side of the jetstreams that separate equatorial from polar air masses as the jets get pushed poleward in the warming world.
The increased vigour and zonality of the jets necessarily involves greater temperature contrasts either side.
We clearly saw more poleward jets during the late 20th century warming spell and the Antarctic became colder.
If the poles warmed so much more than the equator then the pole to equator temperature differential would become smaller and the jets would become weaker, more meridional and more equatorward which has not been seen to happen except during cooling periods such as the LIA (and now?).
So, the pattern actually seems to be little (if any) warming at the equator, cooling at the poles and most warming on the equatorial side of the mid latitude jets with an enhanced temperature contrast across more poleward jets.
I would guess that at a certain level of jetstream vigour and zonality the enhanced westerly flow would start to inhibit the currents flowing poleward past Spitzbergen thus cutting off the flow of warm water into the Arctic and thereby producing the scenario described in the above findings with a permanent summer long ice cap at the Arctic pole.
“The reverse would appear to be also true as during an ice age the Arctic is warmer. Settlements of surprisingly large populations in the arctic from the time of the last ice age, and the transit of people into North America would support the fact.”
Correct in my opinion. More meridional jets allowing more warm air into Arctic regions so the pattern then would be little (if any) cooling at the equator, most cooling on the equatorial side of the mid latitude jets with a reduced temperature contrast across more equatorial jets.
That way natural climate change gives us colder mid latitudes with more snow and ice cover during ice ages but with warmer poles and during interglacials we see warmer mid latitudes with less snow and ice cover and colder poles.
The Arctic behaves differently to the Antarctic and bucks the cooling trend during a general warming period but only until enhanced westerlies disrupt the poleward flow of warm water into the Arctic Ocean.
That scenario seems to fit all the observations I am aware of.
@Stephen Fisher Wilde
I came to the same conclusion, warmer periods give a more zonal jet and extended periods of positive AO, trapping the cold air in the Arctic, and also giving less poleward transport of warmer waters. The differential can be seen clearly in monthly anomalies between the *lower trop’ N. Pole ocean* temperature: http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt
and CET: http://climexp.knmi.nl/data/tcet.dat
Compare first the colder and warmer CET winter months with the LT, then have a look what happens at summer month extremes too.
This may also imply that cooler mid latitude summer months could also see greater Arctic summer ice loss.
vukcevic says:
June 16, 2012 at 12:50 am
it doesn’t appear to be harmonic/sub-harmonic of the solar output, so I concluded it has to be a local resonance associated with effect of two NH’s poles.
Again, you are spouting nonsense. There are no resonances associated with ‘two poles’. What you see at the surface is not at all what is present in the core where the generation and maintenance of the field takes place. ‘Local’? The only thing that makes sense is ‘local’ in the core. The surface is just an arbitrary location.
It is not so hard to envision a tight, zonal flow that would keep the cold locked up in the arctic. What I want to see modled is a flow that would only warm the Vikings in Greenland, and have the MWP happen no other place. When I was asked to swallow that idea I gagged.
My understanding is that they did attempt to modle a flow that looped up to Greenland and back down, and stayed that way for a couple hundred years, but the computer began smoking and then exploded.
johnpnts says:
Capitalism unrestrained has no regard for its worldwide impacts …
Totalitarianism also has issues with its track record and “worldwide impacts” on millions of human beings killed for political expediency. Feel like snuggling up to Hitler, Stalin, Mao etc. in your prescription for ideal world government? Bring it on, mate. Adolph Hitler is the founder of your modern green movement. We kicked over your fascist sand-castles last time with the help of the Russians, and by God we’ll do it again.
Then the question is as to what causes the changes in the AO and AAO to lead the jets to become more meridional or zonal.
Recent observations of the quiet sun relative to that of the late 20th century strongly suggest that the positivity or negativity of the polar oscillations is solar induced.
Stephen Wilde says:
June 16, 2012 at 8:41 am
Then the question is as to what causes the changes in the AO and AAO to lead the jets to become more meridional or zonal.
Presumably this study into the divergent Eemian climate and the absence of the North Atlantic Drift (NAD) points to the strong climate-driving influence of ocean currents, rather than atmospheric winds. Bill Illis for instance reminds us that the current glacial epoch was started about 20 MYa by the isolation of Antarcica and establishment of the southern circumpolar current. Of course there must be some teleconnection between ocean currents and the jet streams and atmospheric oscillations. This no doubt goes both ways but I would have thought the story here is more about ocean currents’ influence.
“I would have thought the story here is more about ocean currents’ influence.”
That is certainly involved since warmer SSTs in the tropics will push the jets poleward making them more zonal in the process.
However we are seeing that the level of solar activity also affects AO and AAO.
Thus my proposal that we have to integrate both influences such that the average position of the jets at any given time is a consequence of the netted out interaction between both bottom up oceanic and top down solar influences.
In the longer term solar effects have primacy because they supply the oceanic energy content in the first place.
Good comment, but those two words are not the same, in pronunciation, meaning or spelling.
And because they are external to the planet’s dynamics. Internal processes, one way or the other, are zero-sum, robbing Peter to pay Paul.
Brian H says:
June 18, 2012 at 4:17 am
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More of your persistent nonsense.
[Moderator’s Note: This is becoming too personal. Disagree agreeably, play nice and engage substantively. Both of you. -REP]