[SunkenCiv]

Until about 1.2 million years ago, ice ages in the Northern Hemisphere occurred about every 40,000 years, says Jerry F. McManus, a paleoclimatologist at Lamont-Doherty Earth Observatory in Palisades, N.Y. But for the past 500,000 years or so, ice ages have occurred, on average, only once every 100,000 years, he notes.

Thanks neverdem.

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[slowhandluke]

Until about 1.2 million years ago, ice ages in the Northern Hemisphere occurred about every 40,000 years, says Jerry F. McManus, a paleoclimatologist at Lamont-Doherty Earth Observatory in Palisades, N.Y. But for the past 500,000 years or so, ice ages have occurred, on average, only once every 100,000 years, he notes.

That's one way to say it. The other is that the warm inter-glacial periods used to show up every 40,000 years and now it's every 100,000 years. It isn't that cold isn't arriving so often, it's that the cold stays around so much longer when it is here.