| Summary: | Hammer and Jouzel presented recent research on climate change in paleogeological times, focusing on results form ice cores in Greenland (Hammer) and the Vostok core in Antarctica (Jouzel), but also drawing on information from ocean sediment cores and other paleoclimate sources. The ice cores provide a richly detailed record of climate and climate change over a period extending back to 200,000 years before present (BP). Annual layer counting is used to precisely date the two Greenland cores down to ca 40 kyr BP. For earlier periods an age model is used. At Vostok the age model is used from the surface because the accumulation is too low for the annual layers to be counted. For Greenland cores, there has been discussion of possible errors due to folds or other disruptions associated with ice flow for the deepest layer especially over the previous interglacial (Gemian). Principal features in ice cores examined include isotopic abundances of oxygen 18 and D in water, and concentrations of chemicals especially hydrogen ion (acidity), sulfur oxides, nitrogen oxides, methanesulfonic acid (MSA) and dust.
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