There have been three major glaciations over the last half billion years (the Phanerozoic) during which multicellular life has existed. They are the end-Ordovician, the end-Carboniferous and the current Pleistocene. After climate scientists (surviving ones at least) subscribed to the interpretation that CO2 dominantly controls global temperature, the Ordovician glaciation 444 million years ago became problematic because it is a deep glaciation that occurred while atmospheric CO2 was high.
Not only high – detailed geological reconstruction by Seth Young and colleagues from the USA, Canada and Estonia has shown that atmospheric CO2 increased in concentration as the end-Ordovician glaciation spread.
Mass spectroscopy, specifically the measurement of carbon 12-13 isotope ratios, is central to reconstructing what exactly happened during this apparently anamalous glaciation. Mass Spec is a core methodology for palaeo climate reconstruction, and is one of the most important technologies in climate science for that reason.
The above linked study by Seth Young and colleagues performed an accurate and controlled reconstruction of carbon geochemistry over the Ordovician-Silurian ice age by looking at the 12/13 carbon ratio in both organic carbon and inorganic carbonate.
Here’s what they found:
The observed change in 13C through the Hirnantian Stage in Estonia and Anticosti Island can be interpreted to reflect atmospheric pCO2 levels that were relatively low immediately prior to the d13Ccarb excursion and then increased as ice sheets expanded (Figs. 5 and 6). Ultimately, this period of elevated pCO2 is followed by global deglaciation.
Note CO2 increased as ice sheets expanded.
This is not possible if CO2 is as dominant of global temperature as climate science currently believes. The word “ultimately” in the above means that glaciation persisted for a few million years under conditions of high atmospheric CO2. Then the glaciation ended, but this termination cannot have had anything to do with CO2, since an atmospheric cause resulting in no effect for millions of years and then suddenly a warming effect, is not credible.
So climate scientists will work hard to blur and smudge the Ordovician high-CO2 glaciation the same as they blur and smudge the Holocene reconstruted climate and all other geological climate records that contradict the CO2 orthodoxy.
But the facts will remain – the carbon revisionists can’t destroy all the rocks in the world. Evidence such as that discovered by Seth Young and colleagues shows CO2 for what it is – just another parameter in a complex atmosphere-ocean-lithosphere system that goes up and down under multiple influences, but is much more an effect than a cause. Rising CO2 while glaciation spread and deepened, at the end of the Ordovician era, illustrates this fact clearly.