Nature Unbound X – The next glaciation

by Javier

Summary: The IPCC expresses virtual certainty that a glaciation is not possible for the next 50 Kyr if CO₂levels remain above 300 ppm. It is the long interglacial hypothesis. Analysis of interglacials of the past 800 Kyr shows they depend on obliquity-linked summer energy, ice-volume, and eccentricity, and they end at glacial inception after ~ 6000 years of Neoglaciation-type temperature decline. The lag between orbital forcing and ice volume change indicates the orbital threshold for glacial inception is crossed thousands of years before glacial inception, and the Holocene went through that threshold long ago. In the absence of sufficient anthropogenic forcing glacial inception should take place in 1500-2500 years. The long interglacial hypothesis rests on the wrong astronomical parameter, high-equilibrium climate sensitivity to CO₂, and uncertain model predictions of very long-tailed CO₂decay. It is not possible to determine at present if…