From Watts Up With That?

Essay by Eric Worrall

“… We might even be currently living at what would have been the onset of this next glacial period …”

We now know how much emissions have delayed the next glacial period

Changes in Earth’s orbit drive long-term glacial cycles, but a new forecast suggests this ancient pattern is being disrupted for tens of thousands of years due to human-induced global warming

By James Dinneen
27 February 2025

…

Where previous studies tried to link changes in orbit to specific periods like the onset of an ice age, Stephen Barker at Cardiff University, UK and his colleagues took a new tack. They looked at the overall patterns of how glacial periods, also called ice ages, fade and return during the intervening “interglacials”. This enabled them to link changes in orbit with changes in ice – despite fuzziness in the ice record over the past million years.

…

The phasing of obliquity and precession that preceded the Holocene suggests glaciation would be likely to be well underway between 4300 and 11,100 years from now. We might even be currently living at what would have been the onset of this next glacial period. “Of course, that’s only in a natural scenario,” says Barker.

The more than 1.5 trillion tonnes of carbon dioxide humans have emitted into the atmosphere since the industrial revolution are expected to cause enough warming to disrupt this long-term glacial cycle.

…Read more: 

https://www.newscientist.com/article/2470262-we-now-know-how-much-emissions-have-delayed-the-next-glacial-period/

The abstract of the study;

Distinct roles for precession, obliquity, and eccentricity in Pleistocene 100-kyr glacial cycles

STEPHEN BARKER, LORRAINE E. LISIECKI, GREGOR KNORR, SOPHIE NUBER AND POLYCHRONIS C. TZEDAKIS

Abstract

Identifying the specific roles of precession, obliquity, and eccentricity in glacial-interglacial transitions is hindered by imprecise age control. We circumvent this problem by focusing on the morphology of deglaciation and inception, which we show depends strongly on the relative phasing of precession versus obliquity. We demonstrate that although both parameters are important, precession has more influence on deglacial onset, whereas obliquity is more important for the attainment of peak interglacial conditions and glacial inception. We find that the set of precession peaks (minima) responsible for terminations since 0.9 million years ago is a subset of those peaks that begin (i.e., the precession parameter starts decreasing) while obliquity is increasing. Specifically, termination occurs with the first of these candidate peaks to occur after each eccentricity minimum. Thus, the gross morphology of 100-thousand-year (100-kyr) glacial cycles appears largely deterministic.

Read more: 

https://www.science.org/doi/10.1126/science.adp3491

I’m a bit suspicious about claims elevated CO2 levels have disrupted the natural glaciation cycle, because there is no need for the CO2 to be transformed into something else in order to affect a radical change in atmospheric CO2 content.

The amount of CO2 dissolved in sea water is 16x greater than all the CO2 in the air, so current atmospheric CO2 levels are insignificant compared to total ocean CO2 content, even when you include all the CO2 we have added to the atmosphere.

CO2 solubility in water changes rapidly with changing ocean temperature. If Milankovitch insolation changes were to cool a large patch of sea water, the atmospheric CO2 level would plummet, just like it did during the last glacial maximum. A cooler ocean would have no trouble swallowing anthropogenic CO2 in addition to natural CO2, because the carrying capacity of the ocean is so much greater than the amount of CO2 in the atmosphere.

Let’s hope the coal doesn’t run out. We might need it.