What Caused the Ice Ages?

Possibly the biggest climate change ever experienced on earth took place around 700 million years ago.  Temperatures changed by tens of degrees.  There was glaciation close to the Equator.  Sea level dropped by as much as 600 metres, as much of the world’s water was sequestered in vast ice sheets.
 
Yet scientists can’t really pin down the reasons for the Ice Age.  Suggested mechanisms include changes in solar luminosity; changes in the sun’s magnetic field leading to changes in cosmic ray flux in the upper atmosphere, and consequent changes in cloud cover; changes in the solar system’s position in space, passing through denser areas of our spiral galaxy; cyclical changes in the Earth’s orbit, or rotation rate, or the Earth’s tilt on its axis (the Milankovitch Cycles); changes in ocean current circulation resulting from tectonic plate movement; sea ice dynamics; massive volcanic activity leading to atmospheric dust and aerosols obscuring the sun; and the Earth’s changing albedo (reflectivity) with increased ice cover.  It may have been a combination of several or all of these factors.
 
One thing it certainly wasn’t would have been low levels of CO2 in the atmosphere.  Atmospheric CO2 levels were higher than today.  Much higher.  About twenty times higher, in fact.  Yet with that massive atmospheric load of CO2, there was no tipping point, no run-away greenhouse effect.  Just a vast Ice Age.  (See Professor Ian Plimer’s excellent book “Heaven and Earth” for more on this).
 
Contrast this uncertainty over the largest climate changes the world has ever seen, with our modern certainty that the very slight increase in global temperature over the last hundred years is caused by one thing only: man-made emissions of CO2.  Never mind that CO2 is a minor greenhouse gas compared to water vapour (which we can’t even pretend to control).  Never mind that man-made emissions of CO2 amount to only about 3% of the natural carbon cycle.  Never mind that today’s CO2 concentration of around 385 ppm is very low compared to most of the Earth’s history — we actually live in a carbon-deficient atmosphere.
 
Never mind that the slight increase in temperature which we see since 1900 is entirely consistent with well-established, long-term natural climate cycles, or even that in the last ten years, the earth has cooled slightly.  The Independent Newspaper (and others) have said that the science is settled, so that must be it.
 
In fact the tide is starting to turn.  I was astonished to see the BBC’s own Stephen Sackur making a monkey of Gerd Leipold, described as the Leader of Greenpeace, over their preposterous claim that the Greenland ice field could melt by 2030. See http://blogs.telegraph.co.uk/news/jamesdelingpole/100007009/redfaced-greenpeace-insists-we-didnt-make-it-up-we-just-emotionalised-the-issue/   The BBC has been a cheer-leader for climate alarmism, yet even they may be starting to crack.  And sixty German scientists have written to Angela Merkel denouncing the alarmist position, and demanding a re-think on the vastly expensive plans for climate mitigation — which is a non-solution to a non-problem.  See http://www.climatedepot.com/a/2282/Consensus-Takes-Another-Hit-More-than-60-German-Scientists-Dissent-Over-Global-Warming-Claims-Call-Climate-Fears-Pseudo-Religion-Urge-Chancellor-to-reconsider-views
 
As someone wrote on a blog today, this is the first time in history that a massively expensive public policy initiative has been based simply and solely on very fallible computer models which purport to predict the future.  They confidently predict the climate in a hundred years, yet they can’t produce a reliable weather forecast (using similar computers) for 48 hours ahead.  It’s time to call time on the Great Carbon Myth.

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1 Response to What Caused the Ice Ages?

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