However, atmospheric CO2 content plays an important internal feedback role.Orbital - scale variability in CO2
concentrations over the last several hundred thousand years covaries (Figure 5.3) with variability in proxy records including reconstructions of global ice volume (Lisiecki and Raymo, 2005), climatic conditions in central Asia (Prokopenko et al., 2006), tropical (Herbert et al., 2010) and Southern Ocean SST (Pahnke et al., 2003; Lang and Wolff, 2011), Antarctic temperature (Parrenin et al., 2013),
deep - ocean temperature (Elder eld et al., 2010), biogeochemical conditions in the Northet al., 2008).