I have been searching internet for a legitimate source for this graph (I made one like that myself orginally): But this one was found by Skyhunter, so there can be little doubt about it's legimaticy. It shows the comparison of the delta 18O records of the ice cores, which is supposed to be a proxy for temperature. Note that the red greenland graph was here first, followed later by the Antarctic results. Although it puzzled the researchers, it was nevertheless accepted that the different hemispheres seemed to have undergo big temperature differences of about 10 degrees C even within a decade or so, looking at the onset of the warming after the last glacial maximum (19-18 thusand years ago versus 14.5 thousand years ago) and the Bolling Allerod (~14,500-12,700 years ago) - Younger Dryas Oscilations (~12,700-11,600 years ago). See for instance the Two-Mile-Time-Machine of Richard Alley. But it had to be temperature, right? because the Methane concentrations correlated very closely with the Greenland isotopes: source One could also be puzzled already, why the atmospheric (and hence global) signal of the CO2 concentration corrolated (lagged) the local Antarctic Ice core isotopes while the atmospheric (and hence global) signal of the CH4 concentration corrolated with the local Greenland Isotopes. A warming mystery or a methane mystery? But then suddenly there was this publication as introduced by Sylas: http://www.pages-igbp.org/products/...on/science highlights/Clark_2009-2(64-66).pdf which shows that the glacial retreat in the Nothern Hemisphere followed the warming schedule of the southern hemisphere. Apart from that I was attempting to demonstrate here that something was wrong with the warming assumptions of the Northern Hemisphere. So what is the real story of the warming and the story of the CH4 concentrations?