At www.warwickhughes.com/icecore/ … there is a short article on pre-industrial levels of co2 which clearly conflicts with the global warming mantra.
Determination of co2 in polar ice cores are commonly used to estimate co2 atmospheric levels in the past. The author, a professor at the central laboratory for Radiological Protection in Warsaw, Poland, outlines just why ice cores are useless as monitors of co2 and a lot of other things too. For example, in compressed ice cores air bubbles actually disappear under the influence of pressure and gases change into solid clathrates which are tiny crystals formed by interaction of gas with water molecules. When ice cores are retrieved these clathrates have a tendency to go pop – and so on. He describes various other things that make ice cores less reliable than the general public are led to believe. As a laboratory scientist he should know what he is talking about – but you never know.