Earth is warming rapidly today. Yet, predictable variations in Earth’s orbit around the sun should be nudging the planet toward a cooler climate. So what gives?

A new study published in Science by Institute of Arctic and Alpine Research (INSTAAR) fellow Gifford Miller and collaborators found that a modern ice age began at least 1,000 years ago. However, by the 1960s, anthropogenic greenhouse gas emissions overwhelmed the cooling influence of Earth’s orbit, halting the growth of Arctic ice.

“It’s an illustration of the real power of greenhouse gases,” Miller said.

The idea of a “failed ice age” has circulated among paleoclimate researchers for years. But the new study provides physical evidence. Miller and collaborators uncovered an unusual archive of past ice behavior: patches of dead vegetation preserved beneath the Barnes Ice Cap on Baffin Island.

The scientists gathered plant samples exposed at the ice’s retreating edge. Back in the lab, analysis of this long-dead vegetation provided a timeline of when the ice cap grew, shrank, or remained stable over the past thousand years.

Arctic Artifacts

The Barnes ice cap is the only remnant of the Laurentide Ice Sheet, which stretched from present-day Indiana to the Arctic Ocean during the last ice age. If another glaciation were to occur today, the ice cap might serve as a starting point.

Miller was thinking about this history when his team first gathered samples from the ice edge in 2022. Scattered among rocks and debris, patches of long-dead moss and small shrubs emerged from beneath the ice.

The researchers hoped that this vegetation might clarify recent events. Radiocarbon dating would provide a “kill date” for each plant sample, documenting the moment when permanent ice last advanced across each location.

“These mosses were growing on the landscape and then all of the sudden the ice cap expands and covers them,” lead author Nicolás Young of Columbia University’s Climate School said. “That radiocarbon age tells you the timing of when ice killed the plant.”

The scientists’ hypotheses were twofold. First, if a new Ice Age had already started, the preserved plants emerging from the ice should have died within the last 3,000 years. Second, the plants closest to the ice edge should be older than the ones further out— representing a growing ice cap.

Both of these predictions were borne out in the data. The kill dates revealed that the ice cap began growing at least 1,000 years ago. But the new ice age never made it past infancy. The ice reached its greatest extent around 1960, before the trend reversed and the ice cap began shrinking once again.

“It took thousands of years for the ice age to get itself into gear, and then it was halted abruptly,” Miller said. “Without greenhouse gas forcing, we would be moving slowly but steadily into an ice age, with more and more permanent snow and ice on the land and expanding sea ice in the Arctic Ocean.”

Shifting seasons

Gifford Miller holds a clump of dead moss that recently emerged from beneath a melting outlet glacier. Radiocarbon dating will tell the researchers exactly when the glacier advanced across this site, killing the moss. (Courtesy, Giff Miller)

Miller remembers a time when a modern ice age seemed like it might have already arrived. In 1972, he joined an expedition to a remote site south of the town of Qikiqtarjuaq on a small island off the coast of Baffin Island. The plan was to return to town via boat after the sea ice melted in late summer. 

But the sea ice never retreated, and the researchers were stranded. Eventually, they hiked out to a military landing strip and hitched a ride on a transport plane.

At the time, Miller saw the unusually cold season as a harbinger of an imminent icy era.

“There was no question that summers were cooling overall from about the 1950s through the mid 1970s,” Miller said. “There was a whole article in Newsweek foretelling the coming glaciations."

By the end of the decade, the science magazines were telling a different story. A growing body of evidence documented a global rise in temperatures caused by greenhouse gas emissions. Miller saw the evidence on his annual Arctic expeditions — each summer the sea ice seemed to melt out a little earlier.

“By the late ‘70s, the debate was over,” he said. “Green house gas forcing was clearly dominant.”

Setting the record straight

Two decades before, the first scientists to study the Barnes Ice Cap arrived at a uniquely confusing moment. In the 1950s and 1960s, the first published studies documented an exceptionally stable glacier. According to Miller and his collaborators' reconstruction, this era coincided with a rare moment of equilibrium. Competing forces — a decrease in summer sun and an increase in greenhouse gases — had brought the ice cap to a standstill.

“The first studies of the Barnes Ice Cap were in the 50s and 60s,” Miller said. “It turns out this was the only time in history it was ever in equilibrium. It made it into the literature that the ice cap was stable, it never changed — it was a false conclusion built on good data.”

Half a century later, a wealth of plant samples and improved carbon dating methods has finally corrected the record. These early results didn’t represent a static system. Instead, they were a snapshot of a nascent ice age the moment before it was overwhelmed.

The twigs, leaves, and mossy patches emerging from below the Barnes ice cap tell a remarkable story. For more than a thousand years, Earth’s orbital cycles were pushing the planet toward a new glaciation. Then, within a few centuries, greenhouse gas emissions overwhelmed the trend and sent the ice into retreat.

“You have this basic Earth system component that’s been operating very routinely,” Young said. “Humans have essentially stopped that process.”

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