Quote:
Originally Posted by Scott Bird  My own view (short version) is that global warming is a natural Earth cycle - and would happen in any case, but that we are accelerating things by our actions. Instead of happening at some distant point in the future, it's happening now. |
Except that we're adding inputs
over and above the natural cycle, risking pushing the system into a state of runaway* positive feedback from which it will not recover for hundreds of thousands of years.
TheColonel, you are aware that hundreds of years is a
long time compared to the timescale for predicted significant effects of human-induced climate change, aren't you. And that the current decline may not be presaging a reversal at all.
Quote:
The present strong deterioration corresponds to a 10-15% decline over the last 150 years and has accelerated in the past several years; however, geomagnetic intensity has declined almost continuously from a maximum 35% above the modern value achieved approximately 2000 years ago. The rate of decrease and the current strength are within the normal range of variation, as shown by the record of past magnetic fields recorded in rocks.
One should note that no one knows if field decay will continue in the future.
...
Some speculate that a greatly diminished magnetic field during a reversal period will expose the surface of the earth to a substantial and potentially damaging increase in cosmic radiation. However, Homo erectus and their ancestors certainly survived many previous reversals. There is no uncontested evidence that a magnetic field reversal has ever caused any biological extinctions. A possible explanation is that the solar wind may induce a sufficient magnetic field in the Earth's ionosphere to shield energetic particles even in the absence of the Earth's normal magnetic field
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From
here
*Yes,
I know that positive feedback = runaway