by R. Hannon, July 2, 2021 in WUWT

Introduction
This post compares CO₂ ice core measurements from Greenland to those from Antarctica over the last millennium. Paleoclimate studies typically use only Antarctic ice cores to evaluate past CO₂ fluctuations. This is because the entire Greenland CO₂ datasets were deemed unreliable due to chemical reactions with impurities in the ice and therefore have not been used in studies since the late 1990’s. This post will demonstrate that CO₂ data from Greenland ice cores have scientific value and respond to key paleoclimate events such as the Little Ice Age and Medieval Warm Period.

Antarctic Ice Core CO₂ Trends
Antarctic ice CO₂ data is readily available and has been studied extensively (Bauska, 2015, Ahn, 2012, Siegenthaler, 2005 and Rubino, 2019). Most of the focus of recent studies has been on high snow accumulation sites which tend to have higher resolution and less smoothing of the trapped gas age in ice bubbles due to the firn to ice transition. Gas age width and resolution ranges from 10 years in Law Dome ice cores to 65 years in Dronning Maud Land DML. Figure 1 shows CO₂ data from Antarctic high-resolution ice cores over the past millennium.

Ahn et al, 2012, compiled CO₂ records from the West Antarctic Ice Sheet (WAIS) and compared them to other key datasets such as Dronning Maud Land (DML), and Law Dome. Their study recognizes and discusses elevated CO₂ during the Medieval Warm Period (MWP) at 1000 AD, decrease of CO₂ around 1600 AD during the Little Ice Age (LIA) and the subsequent rapid increase beginning around 1850 AD.

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