Re: Dat Ol' Debbil Sun

From: Mike Lorrey (
Date: Wed Nov 21 2001 - 11:19:12 MST

Damien Broderick wrote:
> At 04:13 PM 11/20/01 -0500, Mike Lorrey wrote:
> >1/10% additional solar flux in a year, with no change in albedo or
> >insolation results in 1/10% additional retained heat, plus the next
> >year, and so on.
> I think this is mistaken, as I read the report:
> < roughly follows a 1,500-year pattern, based on analysis of the past
> 12,000 years. But the difference from the top of the cycle to the bottom is
> very small, with less than a 0.1 percent difference in energy levels >
> I.e., +0.00007% per year. But maybe that's not what Bond means, since
> surely so small an effect would be impossible to detect... well, except
> cumulatively, which is what the report seems to claim.

Excuse? How does 0.001 suddenly get an extra few zeros tacked on? I
assume you meant to say 0.0007%, and not 0.00007%, a whole order of
magnitude difference.

Cumulative behavior over time is exactly the point, though. If the cycle
is 1200 years, then even with less than one hundredth of one percent
variance, you will accumulate enough change for several degrees C of
temperature variance over several centuries of time. The most rapid
period of change, if it is a sine wave, would be roughly 300-350 years
after the previous low point. If we assume that we are in the rapid
period now, that means the low point would have been some time around
1650-1700 AD. The previous rapid change period would have been a cooling
period of rapid ice formation, and would have occured 600-750 years
prior to today, which corresponds to the reported rapid growth of ice
around Greenland in the Icelandic Sagas as well as in records in the
Vatican about the attempted visit of the Bishop of Iceland to the
abandoned settlements in Greenland.

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