About 800,000 years ago Earth’s ice age cycle transitioned from being about 41,000 years long to about 100,000 years in duration. During a cycle, Earth’s ice coverage ranges from 10 percent of Earth’s surface to 20–23 percent. This transition, known as the Mid-Pleistocene Transition (MPT), may not seem important, but its highly improbable nature and especially what it means for human civilization has profound significance.
Importance of the MPT
Without the MPT global human civilization at more than a subsistence level would never have begun. More significantly, the MPT has allowed for the eventual existence of a high-technology population of billions of people to know and widely communicate the Creator’s ultimate message for humanity. How?
The MPT made possible warm interglacials, during which ice recedes closer to 10 percent coverage of Earth’s surface, and which last not just 2,000–3,000 years but up to 10,000 years. This allows enough time to launch and sustain global human civilization to a point where billions of humans can live on Earth at one time and possess the technology for everyone to hear and understand the Christian message of how Jesus Christ’s atoning death by crucifixion can reconcile them to their Creator. Two to three thousand years, especially with the temperature instability that was characteristic of the 41,000-year periodicity, would not give the necessary time.
A year ago, I wrote a series of three blogs on the miraculous nature of the MPT.1 In my forthcoming book, Weathering Climate Change, I offer a more complete explanation and description of the MPT.2 Now, a paper published in Nature affirms the conclusions that I drew about the MPT in my blogs and book.3
Eleven geoscientists, led by Princeton University’s Yuzshen Yan, report on their analysis of carbon dioxide and methane concentrations in ice core samples that date from 1.0 to 2.7 million years old. The deepest continuous ice core record of Earth’s past climate comes from EPICA Dome C in East Antarctica. This ice core contains the last 1.5 million annual ice layers. However, the bottom 700,000 layers have been under so much pressure from the top 800,000 layers as to pose a significant challenge to scientists’ attempts to determine a detailed and accurate chronology of Earth’s climate during those 700,000 annual layers. Consequently, EPICA Dome C so far has yielded a detailed, reliable climate record for only the past 800,000 years.
Old Ice Next to a Range of Hills
Recently, glaciologists have discovered old Antarctic ice that is near the surface and, hence, not subject to high pressures. In blue ice regions of Antarctica (the light-blue color results from the ice’s absorption of light and encased air bubbles) a combination of powerful ice flow against a range of high hills and surface ice loss by wind scouring and sublimation (ice directly transforming into water vapor) has brought old ice up near the surface. The Allan Hills region of East Antarctica is one such location (see featured image).
A U. S. Geological Survey team has drilled two ice cores to bedrock in the Allan Hills region. The lowest 30 meters of these cores is 2.7–2.0 million years old. However, for these parts of the cores the dating is uncertain and there is some evidence that layers of ice have been disturbed. Yan’s team determined, though, that the ice layers dating from 1.5–1.0 million years are pristine and yield accurate dates.
In the ice core layers dating from 1.5–1.0 million years Yan’s team carefully measured the abundances of carbon dioxide and methane and the ratio of deuterium (a heavy isotope of hydrogen) to hydrogen. The deuterium-to-light-hydrogen ratio is a proxy for temperature at the time the ice was deposited.
Models for the Transition
Measurements by Yan’s team showed that atmospheric carbon dioxide levels for interglacials both before and after the MPT were similar but that for the glacials they were, on average, 24 parts per million higher before the MPT than after. Yan’s team concluded that their measurements were inconsistent “with hypotheses that attribute the transition into the 100k [-year ice cycle] world to a long-term decline in both interglacial and glacial atmospheric CO2.”4 Instead, they stated that their measures affirmed models that link the MPT to:
- decreases in atmospheric CO2 during glacial maxima caused by enhanced dust delivery to the Southern Ocean,
- changes in global ocean circulation, and
- greater ice sheet size over North America.
In an accompanying commentary Eric Wolff, an Earth scientist at Cambridge University, wrote that “these data force us to look elsewhere for the cause of the longer glacial cycles.”5 Here, Wolff indicates that the leading model explaining the MPT was a long-term decline in atmospheric carbon dioxide levels throughout both glacials and interglacials. However, recent papers published by interdisciplinary research teams that I cited in my three blogs6 have challenged this model.
Evidence for Fine-Tuning
Yan’s team’s findings are consistent with the conclusions I drew in my three blogs and book, with one important exception. I attributed the cause of the MPT to many more simultaneous factors than just the three above. In Weathering Climate Change I describe eleven other factors that also played significant roles.7 However, it appears that Yan’s team did not intend to be exhaustive in listing the causes of the MPT and the three they did list seem to be the most important.
I titled my blogs on the MPT “Miracles of the Mid-Pleistocene Transition” for a reason. The notion that possibly fourteen fine-tuned features of Earth’s ice age cycle simultaneously have combined to give humanity ideal living conditions seems highly improbable, even miraculous. Yan’s team’s research and measurements provide additional justification for the titles and for seeing a Creator’s interventions in Earth’s history to make possible the human story of creation, fall, and redemption.
Featured image: The Allan Hills Region of Antarctica
Image credit: U. S. Geological Survey