In 1997 Raymo was the first to provide observations supporting the orbital forcing hypothesis for glacial/deglacial cycles that did not rely on orbital tuning. The research also suggested that ice sheet dynamics needed to be considered in addition to orbital forcing to explain the observed 100,000 year glacial/deglacial cycles.
New evidence from analyzing fossil plankton shells has revealed that CO2 concentration in the Earth’s atmosphere was about triple current levels around 52 million years ago. It then declined to levels close to current atmospheric CO2 concentration 34 million years ago when Antarctica began to glaciate.
In this new study an analysis of new global ocean and land temperature data with corrections to older shipboard measurements reveals that the temperature trend over the period 2000-2014 does not differ from the temperature trend over the period 1950-1999. It is concluded that the “hiatus” reported in IPCC AR5 is most likely an artifact of older measurement techniques.
A new analysis of Antarctic ice cores shows that at the beginning of the last deglaciation, the start of rising CO2 lagged rising temperature by about 800 years which is consistent with the Southern Hemisphere playing a dominant role in the rise in atmospheric CO2. The concomitant rise in methane appears to be governed by Northern Hemisphere processes.