A New Ice Age Was Beginning. Then Humans Started Burning Fossil Fuels
Ancient plants reveal that the vestiges of the North American ice sheet started expanding a few thousand years ago, but that climate change caused it to reverse course.
The Barnes Ice Cap in Canada's Baffin Island began growing several millennia ago but began rapidly shrinking in the 1960s as carbon pollution rose. Andrew Wickert, an environmental science professor at the University of Minnesota Twin Cities, explains that the research shows humans have already done enough damage to cause the major North American ice sheet to start retreating.
The planet experiences phases of ice extending from high latitudes—known as ice ages—followed by periods of retreat toward the poles. The last ice age ended 12,000 years ago, and the Laurentide Ice Sheet covered much of Canada and extended southward. The Barnes Ice Cap, which covers an area the size of Delaware, is frozen to the bedrock and preserves a vegetal record of what grew beneath it.
Scientists used exposure dating to determine when the ice sheet first reached its modern size around 3,600 years ago. They also studied mosses and lichen that colonized the newly exposed land after the ice retreated, allowing them to track the ice cap's growth and retreat. The ice cap started growing again around 2,000 years ago, but since the 1960s, it has begun retreating significantly at an average rate of 4 meters per year.
This retreat coincides with rapidly increasing carbon emissions worldwide. While the exact mechanisms of ice age formation are still under investigation, the study's findings validate a decades-old hypothesis that climate change is happening and could lead to another ice age.
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