I just looked at the hourly forecast for my city on weather.com. It said it was going to continue snowing for the next 36 hours. If I took one day as my time-scale I’d have to say it looks like we are headed towards the next ice age. Pretty obviously, a day is too short a scale. A year works better. You can say that next year will be much like this year and you won’t be very wrong. But we know from records going back a century or two that there has been a gradual warming. The scientific consensus claims that warming is human-induced. To “prove” their point they cite the recent gradual warming. Their thinking is captured by Mann’s infamous “hockey-stick” graph that showed no warming for a thousand years and a sharp increase over the last century. That graph has been debunked but the scientific consensus group-think talks as if the graph is still accurate.They assume that the current slight warming trend is just going to continue, possibly at an accelerated rate. Their elaborate computer models, that bear as much relationship to reality as a paper dart to a Boeing 747, are tweaked to deliver the results they want. In reality, assuming the warming trend will continue indefinitely is as useful as assuming that just because it is snowing today it will carry on snowing.

If we go back to Mann’s Hockey Stick and replace it with a chart closer to reality we find that temperatures have warmed and cooled in cycles lasting a few hundred years. We’ll learn that it was warmer than it is today 900 years ago during the “medieval warm period” and colder during the “little ice age”. If we look at the historical records of life during those periods we find that the warmer period was far preferable to the cooler period. On the scale of a thousand years, the current warming phase does not seem to be out of the ordinary. Average global temperatures fluctuated by about 1° C over the millenium.

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Lets step back by another order of magnitude. What does the weather look like over the last 18,000 years? The next chart shows temperatures rising by about 4° C over the first ten thousand years and then fluctuating on the time scales seen over the last 1000 years. It peaked about 6,000 years ago, about 1° C higher than today.

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That steady rise is a worry, though. What lies before that rise. Stepping back again, we get to the final chart that covers the last 800,000 years. Now we can see a pattern. This paper, Global Warming: A Chilling Perspective, explains:

over the past 800,000 years the Earth has undergone major swings in warming and cooling at approximately 100,000 year intervals, interrupted by minor warming cycles at shorter intervals. This represents periods of glacial expansion, separated by distinct but relatively short-lived periods of glacial retreat.

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The answer to the question, “what time scale should be used when discussing global warming?” is around a million years. And, when we get to that answer we’ll get to a far more important question. What will we do about the next ice age when it really will snow for the next 36 millenium and bury my snow-belt city under a mile-thick sheet of ice?