ScienceDaily: Why an Ice Age Occurs Every 100,000 Years: Climate and Feedback Effects Explained

The magical model that creates cyclic ice ages from practically nothing

Paleoclimate modelers believe they have finally solved the mystery of the ice ages. Evolutionary climatologists currently propose that, in addition to extremely ancient ice ages, about 40 ice ages have occurred over the past 2.6 million years, the most recent starting 100,000 years ago and regressing 20,000 years ago.1 Many theories have been proposed in an attempt to explain how ice ages could develop, and some have even been cast aside and resurrected later. The currently popular idea—based on mathematician Milutin Milankovitch’s 1941 model—is one of those, having been favored since the 1970s despite its admittedly extreme inadequacies. Paleoclimatologists using a combination of computer models believe they’ve finally figured out a way to make Milankovitch’s model work.

A Cold Case?

The earth’s orbit around the sun varies ever so slightly. Milankovitch proposed that the resulting variations in insolation—the sunlight striking the earth—caused a series of ice ages. His model was initially rejected because “this orbital variation by itself is far too weak to actually drive the buildup and decay of the ice sheets.”2 Climate models based on extrapolation of these variations over long ages cannot produce a sufficient drop in temperature to sustain snow through the summer at northern latitudes. Neither can they explain how sufficient snowfall occurred to accumulate ice sheets, since a persistently cold temperature would have decreased precipitation, as cold air cannot contain great amounts of water vapor.

Climate researchers have long sought for “a host of positive feedbacks”1 magnifying these inconsequential orbital variations in order to glaciate about 30% of the earth’s surface at mid and high latitudes. Another major deficiency in the Milankovitch model is its inability to explain the rapid regression of the ice sheets. The latest candidate to create a cycle of ice ages—or at least to explain the one that presumably started 100,000 years ago—is a computer model reported in Nature by University of Tokyo’s Ayako Abe-Ouchi and colleagues.

“Milankovitch's idea that insolation [variations in sunlight striking the earth] determines the ice ages was right in principle,” says climatologist and coauthor Heinz Blatter. “However, science soon recognised that additional feedback effects in the climate system were necessary to explain ice ages. We are now able to name and identify these effects accurately.”

The model Blatter and Abe-Ouchi’s team developed superimposes the effect of a 23,000-year cyclic wobble in the earth’s spin on one other very minor orbital variation in an effort to magnify the impact of decreased sunlight striking the northern latitudes. They believe their model cools the north enough to explain how winter snows could survive the summer melt for tens of thousands of years. The modelers did try to figure in the effect of the altered topography of an ice-covered earth and other factors like the effect of reflectance of the sun’s light by the ice. As with most climate models, the effect of carbon dioxide-induced global warming is included but is calculated to be irrelevant.3 However, they do not address the question of how the precipitation increased enough in a cold climate to produce lots of snow in the first place.

To explain the comparatively rapid regression of continental ice sheets, they suggest that the gradually increasing weight of the ice sheet, which was slowly moving southward, would cause the ground to sink, effectively decreasing the height of the ice sheet and substantially lowering the altitude to a warmer one by the time it reached more southerly latitudes. They propose this would then initiate rapid melting. This process is called delayed isostatic rebound.

“If an entire continent is covered in a layer of ice that is 2,000 to 3,000 metres thick, the topography is completely different,” says Blatter. “This and the different albedo [reflectance] of glacial ice compared to ice-free earth lead to considerable changes in the surface temperature and the air circulation in the atmosphere.”

Simulating the Past? Really?

Like the other components of this model, delayed isostatic rebound is not a new idea, but previous modelers have been unable to make it work out in simulations. Abe-Ouchi’s model combines computer simulations—“multiple snapshots”4—of the presumed 400,000-year history of northern hemisphere glaciation with extrapolated calculations of the earth’s orbit and wobble to produce an apparent explanation for cyclic ice ages. The researchers consider their model to be predictive of past reality. They believe it reflects reality because it is internally consistent with the assumptions on which it is based. The model is fed with data reflecting what is commonly held among climatologists about earth’s conditions hundreds of thousands of years ago; naturally it ends up appearing to confirm that information.

The presumptions on which these computer simulations depend, however, are worldview-based, unverifiable claims about earth’s past. Milankovitch’s model was originally rejected by the scientific community because the calculated differences in sunlight are simply too small to cause ice ages. The model acquired its current popularity because the ice ages proposed by Milankovitch appear to coincide with data from marine sediment and ice cores, yet those very interpretations are worldview-dependent and ignore other explanations. And because each method used to clock the ice ages assumes that the earth is billions of years old, the results appear to reinforce each other. Meteorologist and creation scientist Michael Oard explains, “The Milankovitch mechanism has completely taken over thought. It survives because of circular reasoning.”

The “new” model, Oard points out, is oversimplified in many ways and uses many estimates for unmeasurable variables. Pennsylvania State University paleoclimatologist David Pollard comments that there is no direct interactive link between the ice sheet model and climate model. Such sophisticated computer modeling, Pollard says, must “wait for greater computer power to become available.”2 And University of Calgary glaciologist Shawn Marshall notes “the oversimplified treatment (or absence) of ice sheet–ocean interactions, basal flow (ice-sheet sliding and subglacial sediment deformation) and ice-stream processes in the authors’ simulations. Furthermore,” he said, their atmospheric model’s “ice-sheet melt rates are estimated only from air temperature, and are not based on energy-balance physics.”1

Explaining these deficiencies, the study’s authors write, “It is not practical to run GCMs [general circulation models of atmospheric conditions] with fully coupled ice-sheet models on glacial-interglacial timescales.”5 Therefore, Oard explains, the authors say they “parameterized the ice sheet module. A parameterization is an estimate of the relationship, in this case between atmospheric variables and ice buildup. These parameterizations need ‘verification’ from proxy data, which already have biases involved.” Oard adds that these models “cannot parameterize all that well for clouds, ocean processes, ice aging changes in reflectivity, and solar and infrared radiation. The parameterizations for these variables add error to a model which usually builds with time.” Abe-Ouchi expresses faith in her team’s model but admits more work remains to be done, adding, “Of course I have a strong intuition and confidence that it was OK.”2

The climate models demonstrating the development and regression of ice age conditions and models of earth’s supposed glacial and interglacial topography for the past 400,000 years are all based on unverifiable assumptions about the past. Even if the computer models were sufficiently sophisticated to actually allow multiple parameters to interact, those parameters would be drawn from unverifiable worldview-based assumptions about the unobservable past conditions. The authors attempt to explain how many ice ages developed, assuming that many actually occurred. Yet earth’s geology only shows definitive evidence for one Ice Age. The occurrence of multiple ice ages, like the idea that the earth is billions of years old, is a worldview-based interpretation, not a demonstrable fact.

Just the Facts

As for observable facts, it is true that the earth’s orbit, tilt, and spin vary slightly. These variations are insignificant within the biblical age of the earth. However, if those variations are extrapolated over billions of years, our orbit would vary between a slight ellipse and a circle every 100,000 years, the tilt of our axis would vary on a 41,000 year cycle, and our axis would wobble on a nearly a 23,000 year cycle. Such cycles have never been fully realized of course because God created the earth only about 6,000 years ago.

While evolutionary scientists struggle to explain the origin of many long hypothetical ice ages while not actually explaining even the one that left its impressive marks on earth’s surface, the biblically documented global Flood—which is memorialized in the fossil record—actually does explain how one Ice Age occurred. Increased tectonic activity with associated volcanic eruptions—described in the Bible as the “fountains of the great deep” breaking up (Genesis 7:11)—would have heated the ocean waters causing much greater evaporation of water. The volcanism would also have blasted enormous amounts of dust into the air, blocking much sunlight and cooling the world. (Ice cores do reveal evidence of much volcanic activity during the Ice Age.) Cold continental masses and air containing an enormous amount of water vapor is the necessary combination to produce the amount of snow required to rapidly build up the ice sheets of the Ice Age.

And how, in a Flood geology model, did Ice Age conditions diminish? Without the ongoing enormous levels of volcanic activity and warm ocean water associated with the global Flood, the summers would have warmed and the air dried, reversing ice sheet buildup and causing slow melting at first and then catastrophic melting.

Because uniformitarian ideas about geology preclude the possibility of a recent catastrophic global Flood and one single Ice Age triggered by it, secular geologists propose multiple ice ages occurred. But with a meteorological model founded in biblical history, the single Ice Age makes sense.

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Footnotes

  1. Shawn J. Marshall, “Solution proposed for ice-age mystery,” Nature 500 (8 August 2013): 159–160. Back (1) Back (2) Back (3)
  2. Richard A. Kerr, “How to Make a Great Ice Age, Again and Again and Again,” Science 341 (9 August 2013): 599. Back (1) Back (2) Back (3)
  3. “Carbon dioxide is involved, but it is not determinative.” Ayako Abe-Ouchi, Fuyuki Saito, Kenji Kawamura, Maureen E. Raymo, Jun’ichi Okuno, Kunio Takahashi, and Heinz Blatter, “Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume,” Nature 500 (8 August 2013): 190–194. Back
  4. Shawn J. Marshall, “Solution proposed for ice-age mystery,” Nature 500 (8 August 2013): 159–160. The authors report they used “discrete GCM snapshots to obtain a climate parameterization.” (Ayako Abe-Ouchi, Fuyuki Saito, Kenji Kawamura, Maureen E. Raymo, Jun’ichi Okuno, Kunio Takahashi, and Heinz Blatter, “Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume,” Nature 500 (8 August 2013): 190–194.) Back
  5. Ayako Abe-Ouchi, Fuyuki Saito, Kenji Kawamura, Maureen E. Raymo, Jun’ichi Okuno, Kunio Takahashi, and Heinz Blatter, “Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume,” Nature 500 (8 August 2013): 190–194. Back