coloured bands in the background . A strength of this record is that it matches well with the glacialinterglacial variability seen in the ice cores ( the grey curve confined to the first million years ). A small number of data points exceed 400 ppm but most are in the range 200-350 ppm . Like many of the other records , there appears to be a declining trend over the 5 m . yr period . Note that the data were obtained by TIMS and are offset from the values measured in the same species by Seki et al . ( 2010 ) so the two data sets are not directly comparable .
viii . Pagani et al . ( 2011 )
Fig . 8 . Alkenone pCO 2 reconstructions ( colours ) against oxygen isotope stack ( grey ) from Pagani et al . ( 2011 ) for the period 20 – 45 Ma . Red line added .
This study spans the Eocene / Oligocene transition ( like Pearson et al . 2009 ) but covers a much wider range of ages . Various data sets from high latitude settings were excluded for reasons discussed in the paper . All the estimates > 26 Ma are above 400 ppm , only the four points from 20-26 are all below this value .