Originally posted by: LegendKiller
Because most Co2 graphs I have seen, not all but most, show something like the Vostok core, then another one, then finally air measurements. They use this as an example of how high CO2 levels are.
However, using a composite graph is crap. Why? Because nobody knows what the base level of the other graphs are throughout time.
For example, if the Vostok core showed a range of 1-100 with an average of 50, another core my have a range of 50-150 with an average of 100, and an air measurement may have 100-200 with an average of 150. You can't just slap them together consecutively, because they have different ranges, different compositions, and are taken in different places.
For example, one of the graphs posted frequently shows Vostok, another dome (forgot which) and Mauna Loa air samples. How can these be tied together completely? Air measurements in one area can't be totally compared to another. Consider the different environments. The Vostok cores are far away from vegitation or volcanos, whereas Mauna Loa is near vegitation and also volcanos. Furthermore, one is a direct air sample while the other isn't.
You can keep going, showing how the total sample utilized and the conclusions made from the consecutive time-slicing/splicing/combining of these samples can lead to a corrupt conclusion.
Please provide a link to the graph you are talking about.
As for the location of the sampling. CO2 has a residence time in the atmosphere of 100-200 years or so. Because of this very long residence time the CO2 has time to diffuse evenly in the atmosphere, so one can take a measurement of CO2 at different parts of the globe and obtain similar concentrations. It isn't like smog which is a localized pollutant. This is why one can actually measure the seasonal change in CO2 in the atmosphere (due to vegetation changes throughout the seasons) from the top of a Volcano in Hawaii (which does not experience much seasonality with its vegetation growth). This is why the Keeling curve undulates during the course of every year.
http://en.wikipedia.org/wiki/Keeling_curve