Paleoclimatologist: Many researchers assume that variations in stomatal density on fossilized leaves directly index ancient atmospheric carbon dioxide concentrations. However, recent controlled botanical experiments demonstrate that ambient humidity and soil salinity induce alterations in stomatal density indistinguishable from those caused by carbon dioxide fluctuations. Therefore, stomatal density measurements from fossilized leaves cannot reliably serve as standalone proxies for prehistoric atmospheric carbon dioxide levels.
What is the primary conclusion of the paleoclimatologist's argument?
Answer: Stomatal density measurements from fossilized leaves cannot reliably serve as standalone proxies for prehistoric atmospheric carbon dioxide levels / Stomatal density measurements cannot reliably serve as standalone proxies for prehistoric atmospheric carbon dioxide levels / Stomatal density cannot reliably serve as a standalone proxy for ancient atmospheric carbon dioxide levels / Stomatal density alone cannot reliably determine ancient atmospheric carbon dioxide concentrations / Stomatal density cannot reliably serve as a standalone proxy for prehistoric carbon dioxide levels / Fossil stomatal density cannot reliably serve as a standalone proxy for atmospheric carbon dioxide / Stomatal density is not a reliable standalone proxy for prehistoric carbon dioxide levels / Stomatal density alone is not a reliable proxy for ancient carbon dioxide