Researchers at Alfred Wegener Institute expand prevailing theory on climate history
Climate researchers at the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association (AWI) expand a prevalent theory regarding the development of ice ages. In the current issue of the journal Nature three physicists from AWI’s working group “Dynamics of the Palaeoclimate” present new calculations on the connection between natural insolation and long-term changes in global climate activity. Up to now the presumption was that temperature fluctuations in Antarctica, which have been reconstructed for the last million years on the basis of ice cores, were triggered by the global effect of climate changes in the northern hemisphere. The new study shows, however, that major portions of the temperature fluctuations can be explained equally well by local climate changes in the southern hemisphere.
The variations in the Earth’s orbit and the inclination of the Earth have given decisive impetus to the climate changes over the last million years. Serbian mathematician Milutin Milankovitch calculated their influence on the seasonal distribution of insolation back at the beginning of the 20th century and they have been a subject of debate as an astronomic theory of the ice ages since that time. Because land surfaces in particular react sensitively to changes in insolation, whereas the land masses on the Earth are unequally distributed, Milankovitch generally felt insolation changes in the northern hemisphere were of outstanding importance for climate change over long periods of time. His considerations became the prevailing working hypothesis in current climate research as numerous climate reconstructions based on ice cores, marine sediments and other climate archives appear to support it.
AWI scientists Thomas Laepple, Gerrit Lohmann and Martin Werner have analysed again the temperature reconstructions based on ice cores in depth for the now published study. For the first time they took into account that the winter temperature has a greater influence than the summer temperature in the recorded signal in the Antarctic ice cores. If this effect is included in the model calculations, the temperature fluctuations reconstructed from ice cores can also be explained by local climate changes in the southern hemisphere.
Thomas Laepple, who is currently conducting research at Harvard University in the US through a scholarship from the Alexander von Humboldt Foundation, explains the significance of the new findings: “Our results are also interesting because they may lead us out of a scientific dead end.” After all, the question of whether and how climate activity in the northern hemisphere is linked to that in the southern hemisphere is one of the most exciting scientific issues in connection with our understanding of climate change. Thus far many researchers have attempted to explain historical Earth climate data from Antarctica on the basis of Milankovitch’s classic hypothesis. “To date, it hasn’t been possible to plausibly substantiate all aspects of this hypothesis, however,” states Laepple. “Now the game is open again and we can try to gain a better understanding of the long-term physical mechanisms that influence the alternation of ice ages and warm periods.”
“Moreover, we were able to show that not only data from ice cores, but also data from marine sediments display similar shifts in certain seasons. That’s why there are still plenty of issues to discuss regarding further interpretation of palaeoclimate data,” adds Gerrit Lohmann. The AWI physicists emphasise that a combination of high-quality data and models can provide insights into climate change. “Knowledge about times in the distant past helps us to understand the dynamics of the climate. Only in this way will we learn how the Earth’s climate has changed and how sensitively it reacts to changes.”
To avoid misunderstandings, a final point is very important for the AWI scientists. The new study does not call into question that the currently observed climate change has, for the most part, anthropogenic causes. Cyclic changes, as those examined in the Nature publication, take place in phases lasting tens of thousand or hundreds of thousands of years. The drastic emission of anthropogenic climate gases within a few hundred years adds to the natural rise in greenhouse gases after the last ice age and is unique for the last million years. How the climate system, including the complex physical and biological feedbacks, will develop in the long run is the subject of current research at the Alfred Wegener Institute.
Notes for editorial offices:
Your contacts at the Alfred Wegener Institute are Prof. Gerrit Lohmann (Tel: +49(471)4831-1758; e-mail: Gerrit.Lohmann@awi.de), Dr. Martin Werner,Tel: +49(471)4831-1882; e-mail: Martin.Werner@awi.de) and Dr. Thomas Laepple (Thomas.Laepple@awi.de). Your contact in the Communication and Media Department is Ralf Röchert (Tel: +49 (0)471 4831-1680; e-mail: medien@awi.de).
The original title of the publication to which this press release refers is: Laepple, T., M. Werner, and G. Lohmann, 2011: Synchronicity of Antarctic temperatures and local solar insolation on orbital time scales. It will be published in the magazine Nature on 3 March 2011 (doi:10.1038/nature09825).
You will find printable pictures at: www.awi.de
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and mid latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctica. The Alfred Wegener Institute is one of the seventeen research centres of the Helmholtz Association, the largest scientific organisation in Germany.
“To avoid misunderstandings, a final point is very important for the AWI scientists. The new study does not call into question that the currently observed climate change has, for the most part, anthropogenic causes.”
Why? Do they call women’s right to vote into question? I guess not, because, if not for a better reason, the topic of their study has nothing to do with it. But, but
But then why don’t they say so clear and firm? Is it not important for AWI scientists? Just to avoid misunderstandings (and politically correct accusations like “male chauvinist pigs” of course). Why are they so sure women don’t have a say in their funding?
/And now… sarc off
Fred H. Haynie says:
March 4, 2011 at 8:56 am
I agree that CO2 is not a good proxie for temperature, but that is what CAGW is all about, climate sensitivity. The divergence shows that it is not a good proxie. Are you trying to say that climate sensitivity is greater or lesser to anthropogenic sources than natural sources?
A little careful with the definitions, please. CAGW is about climate sensitivity for CO2, not about CO2 as proxy for temperature. That is only possible if CO2 was the only driver. But I agree that the sensitivity is not large and probably overwhelmed by natural variability.
There is no significant longitude effect on background levels of CO2. At the same latitude and season, the concentrations are the same over land and over sea. There is a lot more sea doing it’s thing than trees in the mid latitudes doing their thing.
Indeed, the seasonal variations differ more with latitude and altitude, the latter is visible here:
http://www.ferdinand-engelbeen.be/klimaat/klim_img/seasonal_height.jpg
A large part of the ocean CO2 releases and sinks is not seasonal at all: constantly emitting at the Pacific Equator (upwelling of deep ocean water by the THC), constantly absorbing in the NE Atlantic at the THC sink place. See the winter/summer dpCO2 over the oceans at:
http://www.pmel.noaa.gov/pubs/outstand/feel2331/maps.shtml
Thus, indeed the seasonal variation of the oceans is mainly in the mid-latitudes. That means that the emissions from the oceans and the absorption by the biosphere in summer have their highest countercurrent action, but clearly vegetation wins, as total CO2 sinks and d13C/O2 increases.
Ferdinand,
The rates of sources and sinks is not constant any where on earth. As Spencer and I have shown you. Those rates are always changing with changing skin surface temperatures. The changes in the Arctic sink are great and that is what is mostly changing the CO2 concentrations, not trees. Also consider the effects of water absorption and evaporation on the fractionation of C12/C13.
Fred H. Haynie says:
March 4, 2011 at 4:44 pm
The rates of sources and sinks is not constant any where on earth. As Spencer and I have shown you. Those rates are always changing with changing skin surface temperatures. The changes in the Arctic sink are great and that is what is mostly changing the CO2 concentrations, not trees. Also consider the effects of water absorption and evaporation on the fractionation of C12/C13.
If you look at the Feely charts in the previous comment, you will see that the Arctic shows less deep negative pCO2 area, but near all NH mid-latitude oceans are negative. Thus most of the NH oceans are absorbing far more CO2 in winter, at the moment that average CO2 levels increase. The opposite happens in summer.
The d13C fractionation by releasing and absorbing CO2 in the oceans gives a drop of about 8 per mil d13C. For average ocean surface waters at ~+1 to +2 per mil, the ocean-air equilibrium would be around -6.5 per mil. That is the pre-industrial equilibrium found in ice cores. The current atmosphere is at -8 per mil. Any extra addition of CO2 from the oceans would slightly increase the per mil of the atmosphere. But during the summer we see a huge increase in d13C and a huge decrease in winter. That can’t be caused by the oceans, as the change is too large.
Based on oxygen balance, we have a good insight how much CO2 is released and taken away by vegetation over the seasons. That fits the CO2 and d13C balance quite well, the difference being what the oceans do. So the seasonal variations are dominated by vegetation (or why should the SH show less seasonal variation, if sea ice was the cause?), while the long term trend is dominated by fossil fuel emissions, as oceans and vegetation both act as sinks.
Ferdinand,
Your last statements are based on the false assumption that there are no long-term changes in the oceans’ sources and sink rates.
Well let me see here; if I have a billion dollars to do climate research; hey make that ten billion, and I can use some of that money to put up a replacement CO2 satellite; or a sulphuric acid satellite or maybe both; and we already built those so we just have to make a copy; no reseach required.
Or I could spend the money hiring people to dig in the mud, or bore holes in the ice in Antarctica; and I now know that these researches don’t have anything whatsoever to do with Man Made Catastrophic Climate Disruption due to anthopogenic GHGs, or man made GHGs either; so ‘splain me; why am I going to pay money to continue these studies that simply refute what some old nutcake wrote over a century ago, that we now know was rubbish.
I should pull the plug on this research and get all those folks out of Antarctica, so the Emperor Penguins don’t get hog tied so the leopard seals can catch them.
So do I need the sulphuric acid satellite or the CO2 one. Izzere someone other than those goofballs, who can’t undo a cone fairing, that we could get to launch the satellite for us; maybe the Russians; after all, Sputnik didn’t crash into the ocean. Yes I think some budget readjustments are in order.