I understand the ice cores! Victory is mine!
I appear to have won my mini-war with some denier acquaintances by outflanking them on the battle of the ice cores.
The denier argument goes like this:
"The ice cores show that past temperature rises happened before carbon dioxide concentrations rose, therefore temperature drives carbon and not the other way round, hence man made carbon emissions will not cause temperature rises."
The statement is true, the conclusion is 180° out.
The ice cores show the relationship between temperature and carbon dioxide under natural warming (there were no power stations or SUVs). So something other than carbon pushed up temperature (slowly), leading eventually to the slow release of carbon dioxide and methane (eg from melting permafrost and other climatic changes). This carbon will have then contributed in turn to that warming which lasted for 5000 years before starting to cool again. So we would expect to see what we see in the ice-cores.
The current situation is quite different. Carbon dioxide is rising faster and further than in the ice cores due to man's activity. Temperature rises are lagging behind the carbon rises. Using the deniers' own logic, this lag proves that man-made carbon emissions are driving current temperature rises.
BTW: the full explanation can be seen on the excellent realclimate.org.