It has long been established in the scientific literature (and affirmed by the IPCC) that CO2 concentration changes followed Antarctic temperature changes by about 600 to 1000 years during glacial-interglacial transitions throughout the last ~800,000 years (Fischer et al., 1999; Monnin et al., 2001; Caillon et al., 2003; Stott et al., 2007; Kawamura et al., 2007).
In contrast, two new papers cite evidence that the timing of the lagged CO2 response to temperature changes may have ranged between 1300 and 6500 years in some cases. It would appear that a millennial-scale lagged response to temperature undermines the claim that CO2 concentration changes were a driver of climate in the ancient past.
Temperature correlations between the eastern equatorial
Pacific and Antarctica over the past 230,000 years
“The EEP [eastern equatorial Pacific] stack shows persistent covariation with Antarctic temperature on orbital and millennial timescales indicating tight coupling between the two regions. This coupling however cannot be explained solely by CO2 forcing because in at least one important case, the Marine Isotope Stage (MIS) 5e–5d glacial inception, both regions cooled ∼5–6.5 thousand years before CO2 decreased. More likely, their covariation was due to advection of Antarctic climate signals to the EEP by the ocean.”
“The discovery that atmospheric CO2 covaries with Antarctic temperature and global ice volume (Lorius et al., 1990; Lüthi et al., 2008; Petit et al., 1999) has propelled CO2 to the forefront as climatic “globalizer”. However, the processes governing CO2 variability are themselves poorly understood, and likely require an oceanic/climatic trigger in the first place (Adkins, 2013; Ferrari et al., 2014; Sigman et al., 2010).”
“Antarctic ice core records are furthermore ambiguous with regard to the causal relationship between CO2 and temperature. Phase relationships show CO2 lagging behind temperature in the obliquity band (Jouzel et al., 2007) and across some major transitions (Caillon et al., 2003; Fischer et al., 1999; Kawamura et al., 2007; WAIS Divide Project Members, 2013), most prominently during the Marine Isotope Stage (MIS) 5e–5d boundary, i.e. the last glacial inception. Antarctic cooling at this time was associated with a major Milankovitch signal, and appears to have transpired almost entirely before the change in CO2 concentration. It remains unclear whether the temperature lead was restricted to Antarctica or was broader.”
Asynchrony between Antarctic temperature and CO2
associated with obliquity over the past 720,000 years