What I have objected to is theattempt to link the climate of the southern Antarctic zone to the rest of theworld. It is not obviously plausible because of the prevailing circum polarwind system that isolates the Antarctic. This work shows us that local conditions inside this circumpolar windsystem dominate the ice core record.
It should have been apparent whenthe warming northern Hemisphere went its own way in a way that contradicted aglobal model linking the Antarctic. Takeaway the Antarctic and we have lived through a warming cycle over the pastthree decades.
We need to accept the hugeinfluence of the circumpolar wind system’s ability to seal off Antarctica from the rest and know that this is a blessingthat prevents excessive cold blizzards to ravage deep into the SouthernHemisphere and perhaps lower the global temperature a degree or two.
What I have properly understoodis that the unique geometry of the land surface on Earth does two major things.
1 It seals of the Antarctic cold from been anything otherthan an excess heat dump.
2 It directs the carefully positioned Atlantic tropicalwaters directly into the Arctic Ocean eliminating the north polar Ice Cap.
I have already observed that thekey adjustment was made 12900 years ago.
New Interpretation Of AntarcticIce Cores
by Staff Writers
Thus far many researchers have attempted to explain historical Earthclimate data from Antarctica on the basis ofMilankovitch's classic hypothesis. "To date, it hasn't been possible toplausibly substantiate all aspects of this hypothesis, however," statesLaepple. "Now the game is open again and we can try to gain a betterunderstanding of the long-term physical mechanisms that influence thealternation of ice ages andwarm periods."
Climate researchers at the Alfred Wegener Institute for Polar and MarineResearch in the Helmholtz Association (AWI) expand a prevalent theory regardingthe development of ice ages.
In the current issue of the journal Nature three physicists from AWI'sworking group "Dynamics of the Palaeoclimate" present newcalculations on the connection between natural insolation and long-term changesin global climate activity. Up to now the presumption was that temperaturefluctuations in Antarctica, which have been reconstructed for the last millionyears on the basis of ice cores, were triggered by the global effect of climatechanges in the northern hemisphere.
The new study shows, however, that major portions of the temperaturefluctuations can be explained equally well by local climate changes in thesouthern hemisphere.
The variations in the Earth's orbit and the inclination of the Earthhave given decisive impetus to the climate changes over the last million years.Serbian mathematician Milutin Milankovitch calculated their influence on theseasonal distribution of insolation back at the beginning of the 20th centuryand they have been a subject of debate as an astronomic theory of the ice agessince that time.
Because land surfaces in particular react sensitively to changes ininsolation, whereas the land masses on the Earth are unequally distributed,Milankovitch generally felt insolation changes in the northern hemisphere wereof outstanding importance for climate change over long periods of time.
His considerations became the prevailing working hypothesis in current climate research asnumerous climate reconstructions based on ice cores, marine sediments and otherclimate archives appear to support it.
AWI scientists Thomas Laepple, Gerrit Lohmann and Martin Werner haveanalysed again the temperature reconstructions based on ice cores in depth forthe now published study. For the first time they took into account that thewinter temperature has a greater influence than the summer temperature in therecorded signal in the Antarctic ice cores. If this effect is included in themodel calculations, the temperature fluctuations reconstructed from ice corescan also be explained by local climate changes in the southern hemisphere.
Thomas Laepple, who is currently conducting research at HarvardUniversity in the US through a scholarship from the Alexander von HumboldtFoundation, explains the significance of the new findings: "Our resultsare 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 northernhemisphere is linked to that in the southern hemisphere is one of the mostexciting scientific issues in connection with our understanding of climatechange.
Thus far many researchers have attempted to explain historical Earth climate data fromAntarctica on the basis of Milankovitch'sclassic hypothesis. "To date, it hasn't been possible to plausiblysubstantiate all aspects of this hypothesis, however," states Laepple."Now the game is open again and we can try to gain a better understandingof the long-term physical mechanisms that influence the alternation of ice agesand 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 furtherinterpretation of palaeoclimate data," adds Gerrit Lohmann. The AWIphysicists emphasise that a combination of high-quality data and models canprovide insights into climate change.
"Knowledge about times in the distant past helps us to understandthe dynamics of the climate. Only in this way will we learn how the Earth'sclimate has changed and how sensitively it reacts to changes."
To avoid misunderstandings, a final point is very important for the AWIscientists. The new study does not call into question that the currentlyobserved climate change has, for the most part, anthropogenic causes. Cyclicchanges, as those examined in the Nature publication, take place in phaseslasting tens of thousand or hundreds of thousands of years.
The drastic emission of anthropogenic climate gases within a fewhundred years adds to the natural rise in greenhouse gases after the last iceage and is unique for the last million years. How the climate system, includingthe complex physical and biological feedbacks, will develop in the long run isthe subject of current research at the Alfred Wegener Institute.
Theoriginal title of the publication to which this press release refers is:Laepple, T., M. Werner, and G. Lohmann, 2011: Synchronicity of Antarctictemperatures and local solar insolation on orbital time scales. It will bepublished in the magazine Nature on 3 March 2011 (doi:10.1038/nature09825).
No comments:
Post a Comment