We narrowly missed a new ice age, and now we won’t see one for a long time

Enlarge (credit: Kelsey Winsor)

Recorded human history has played out within one type of climate—an interglacial period. During the glacial periods of the last million years (commonly referred to as “ice ages”), great ice sheets grew to cover Canada and some points south, as well as Northern Europe and much of Russia.

In the 1970s, we learned there was a consistent 100,000-year heartbeat to this back-and-forth cycle governed by subtle patterns in Earth’s orbit. The thing is, it’s about time for the next heartbeat. We’re at the part of the cycle where the interglacial period should be wrapping up and the slow but inexorable descent into another ice age would begin.

But that hasn’t happened, and it’s not going to any time soon. Our current breakneck emissions of greenhouse gases will see to that. Still, the scientific question is worth asking: what, exactly, does it take to start off an ice age?

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