After ten thousand years of a balmy interglacial, during which humans learned to till the soil, smelt metal and write down their history, the next glacial period got started around the time of Christ, built gradually over two thousand years, and then was
brought to an abrupt halt in 1960.
Technically, we've been in the same Ice Age for tens of millions of years, swinging between glacial periods (what most people think of as an Ice Age, with ice sheets over Canada and Northern Europe) and interglacial periods (with smaller polar ice caps, but still ice). In the 1970s, some feared that aerosol pollution would cause
global cooling and plunge us back into another glacial period. They might have been right, if it weren't for those pesky industrialists.
A glaciation is slow—"it would have taken about 30,000 years for anyone to really notice"—but the end of this one was anything but. Researchers at Columbia University studying the remnants of the Laurentide Ice Sheet on Baffin Island have established, by carbon dating the moss trapped under its ice, that it "shrank to its smallest size about 3,000 years ago, then started growing again about 2,000 years ago":
The new research [argues] that the first renewed growth of an ice sheet equals the start of a glacial period, "marking the onset of the next glaciation." That period didn't last long, however. The ice cap reached its maximum extent around 1960, when summer warming caused a "negative mass balance, ice margin recession, and the termination of the next glaciation."
Cumulative global CO2 emissions between the start of the Industrial Revolution and 1960—so, enough to stave off a glaciation—were 308 billion tonnes. By 2024, the cumulative total had reached 1.85 trillion tonnes.
The team expects the [Barnes Ice Cap on Baffin Island] to vanish within a few centuries. Without that icy foundation, it will be harder for new ice to build up. As a result, scientists can't say when (or where) the next glaciation might occur, especially while greenhouse gas concentrations in the atmosphere remain high. ... "That will be the true very last remains of the Laurentide, disappearing for good. ... What has been an extremely natural and predictable phenomenon is now gone."