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Milankovitch cycles consist of three orbital parameters: eccentricity, obliquity, and precession of equinoxes.

According to Milutin Milankovitch, the most recent glacial period ended nearly 11,000 years ago, when combination of eccentricity, obliquity, and precession at that time strongly favored deglaciation in the northern high latitudes. Specifically, eccentricity, moving on cycles of 100,000 years, was slightly larger than it is today, and Earth was slightly elliptical than it is today. Obliquity, moving between 22.1 and 24.5 degrees, was nearly at its maximum 11,000 years ago. And precession was pointing at Vega.

It then goes that this combination of orbital parameters enabled the northern hemisphere to experience its summer solstice at the perihelion, which gave the northern hemisphere the largest possible solar radiation on any summer solstice positions. And obliquity was at its maximum, significantly reducing the size of polar regions shielded from solar radiation between the spring and fall equinoxes in the northern hemisphere. So the northern high latitudes experienced a high volume of incoming solar radiation that allowed snow accumulation rate to fall below that of snow melting. Thus, the most recent glacial period started to end.

But now, 11,000 years after the last glacial period, the combination of orbital parameters changed a lot. Eccentricity is near its lowest, making the total solar radiation on Earth at perihelion and aphelion closer than ever. Obliquity is midway between the maximum and the minimum, shielding a significant area of the polar regions from incoming summer sunlight. And precession is now pointing at the Polaris, the exact opposite of Vega. This combination allows the northern hemisphere to experience its summer solstice at the aphelion, and winter solstice at the perihelion, which significantly curtails the amount solar radiation in the northern hemisphere. The northern high latitudes now are shielded more from solar radiation between the spring and fall equinoxes. These new changes seem to make Earth go in the direction of another glacial period, because snow melting seems to be slowing in the northern high latitudes and snow accumulation quickening.

Throughout geological history, Earth has seen far lengthier and more widespread glacials than interglacials. Indeed, interglacials are just short blips in the geological history. It thus seems reasonable to say we are entering another Ice Age according to Milankovitch cycles.

Glacials and Interglacials in Earth's History

Some of you may cite the current anthropogenic climate change as a rebuttal, but for the question's sake, just ignore it.

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    $\begingroup$ This is a looooong way to ask a simple question... You don't need to explain what Milankovitch cycles are, it's better to go straight to the point. $\endgroup$ – Jean-Marie Prival Jul 15 at 12:34
  • $\begingroup$ note it would not be a new ice age, but a new glacial period in the current ice age we are still in. $\endgroup$ – John Jul 21 at 2:15
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It thus seems reasonable to say we are entering another Ice Age according to Milankovitch cycles.

Some of the Milankovitch conditions would appear to make the Earth ripe for a new glacial epoch starting now, or perhaps a few hundred years ago. In particular, aphelion occurs in early July, and obliquity is low. Both of these make for mild northern hemisphere summers, a key condition needed for snowfall from the previous seasons to linger into fall.

But one other key Milankovitch condition needed to make snowfall linger, orbital eccentricity, argues against a new glacial epoch starting now. The low (and decreasing) eccentricity makes the current dip in summertime insolation at high northern latitudes too small of a dip to trigger the onset of an glacial epoch. Look at the graph you posted in your question. Glacial epochs start when summertime insolation at high northern latitudes drops to very low values. The current local minimum is not low enough to enable widespread accumulation of snow and ice over the summer.

Some of you may cite the current anthropogenic climate change as a rebuttal, but for the question's sake, just ignore it.

Even without anthropogenic help, the current interglacial is likely to last for 50,000 years [Berger and Loutre]. With anthropogenic help, the current interglacial may even last indefinitely [Steffen].

Throughout geological history, Earth has seen far lengthier and more widespread glacials than interglacials. Indeed, interglacials are just short blips in the geological history.

That is true only for last 2.58 million years, possibly the last 34 million years. The Earth has been ice-free for most of the last 550 million years. Ice ages (periods during which ice can form, intermittently, are just short blips.


References:
Berger, André, and Marie-France Loutre. "An exceptionally long interglacial ahead?." Science 297.5585 (2002): 1287-1288.

Steffen, Will, et al. "Trajectories of the Earth System in the Anthropocene." Proceedings of the National Academy of Sciences 115.33 (2018): 8252-8259.
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Orbital cycles doubtlessly play a role in the Quaternary climate record, together with other effects like ice sheet dynamics, but their effect is dwarfed by speed and amount of the current climate change. Even if we were in for a new glaciation from orbital parameters alone (which is not the case), there'd be no use counting on it because they work on longer timescales, reaching from 10s of thousands to millions of years. An answer can, of course, be fleshed out endlessly simply because of the complexity of the processes at work and the increasing knowledge base. Isolating one effect, here M. cycles, likely leeds to misconceptions.

Tl; dr, and to answer the question:

No, we are not due for a new glaciation (not a new "Ice Age", we are in an ice age) from orbital forcing alone.

Citing Ganopolski et. al. Critical insolation–CO2 relation for diagnosing past and future glacial inception

Additionally, our analysis suggests that even in the absence of human perturbations no substantial build-up of ice sheets would occur within the next several thousand years and that the current interglacial would probably last for another 50,000 years.

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  • $\begingroup$ I see. So feedback loops on Earth are also important in triggering both the onset and the end of glacial periods, right? And the Milankovitch cycles only deal with the amount of solar radiation reaching the top of the atmosphere. $\endgroup$ – cienhundred100 Jul 20 at 10:44
  • $\begingroup$ Right in the first part, partly in the second. The effects of orbital forcing are much more complicated, timing plays a role (simplest example eccentricity -> Kepler's 2. law) as well as when and where insolation reaches the earth (latitude, landmass distribution, circulation). The result is not uniform over the globe, we can't exclude effects that shadow or push orbital forcing, and it isn't always detectable in earth's history. $\endgroup$ – user20217 Jul 20 at 16:20

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