A new ice age was beginning thousands of years ago. Remnants of the North American ice sheet had started to expand.
Ancient plants record that shift. They show the ice sheet was growing again after a long retreat.
Then the climate changed course. The expansion slowed and reversed.
Fossil fuel burning played a central role. Human emissions altered the trajectory of the ice sheet.
Researchers reached this conclusion by studying plant remains. The plants preserve a record of past climate conditions.
The findings suggest human activity interrupted a natural cycle. An ice age that was starting never fully arrived.
The study adds to evidence that emissions reshape the climate. It shows how quickly human influence can redirect natural processes.
