Thursday, January 21, 2016

No Ice Age for 100,000 Years.

Back in the 1600s through the beginning of World War One, we were in a slightly icehouse climate called The Little Ice Age. And by rights, we really should be going into another one right now. Just as the news media told us we would be back in the 1970s. But with 405 ppm CO2 (485 ppm CO2e) in the atmosphere we should consider ourselves lucky if it comes about. Because at 280 ppm in the 1880s towards the end of the LIA, which would still be the approximate CO2 content if we hadn't burnt all those fossil fuels, especially coal and petroleum, we would instead be heading headlong into yet another major ice age -- when all of Canada, the USA northern tier, and much of Northern Europe including Russia and Siberia -- would become glaciated: covered with ice up to three miles thick.

We narrowly missed a new ice age, and now we won’t see one for a long time.
by Scott K. Johnson -
13 January, 2016

Before fossil fuels rendered this moot, conditions were nearly right.

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?

We are currently at a low point in summer sunlight reaching the northern high latitude region, which is how the orbital cycles turn into glacial cycles. Because there are several orbital cycles involved, the peaks and valleys in that sunlight are complex—it’s not as simple as a sine wave oscillating between a constant high and a constant low. But there were two interglacial periods in the last million years (one 400,000 years ago and one 800,000 years ago) with a similar combination of orbital cycles. Both crossed the threshold into an ice age when they hit this low point in sunlight.

Now we're going to have a super-long interglacial period for at least 50,000 years, perhaps 100,000 years. And it might include a second Permian Exstinktion [sic!].

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