4 April 2012

CO2 ‘drove end to last ice age’

By Jonathan Amos Science correspondent, BBC News



“Our global temperature looks a lot like the pattern of rising CO2 at the end of the ice age, but the interesting part in particular is that unlike with these Antarctic ice core records, the temperature lags a bit behind the CO2,” said Dr Shakun, who conducted much of the research at Oregon State University but who is now affiliated to Harvard and Columbia universities.

“You put these two points together – the correlation of global temperature and CO2, and the fact that temperature lags behind the CO2 – and it really leaves you thinking that CO2 was the big driver of global warming at the end of the ice age,” he told BBC News.


Sky:  I suggest that we look very carefully at this article.  The findings are anything but conclusive.  The charts showing CO2 and temperature have always shown that they are very closely interwoven.  I am suspicious reading the contents of the quote below.  “CO2 was the big driver of global warming at the end of the ice age”  As Don J. Easterbrook, PhD Emeritus Professor of Geology, Western Washington University. Retired, reminded readers  recently,[ http://wattsupwiththat.com/] correlation does not prove cause.  When two phenomena move together they are often simply driven by the same phenomenon.  We must ask, what drove the driver?  What made the CO2 shift?  Obviously we ask, What made the temperature shift?  There is very little doubt that when in the midst of an ice age, a warming trend strong enough to melt glaciers almost obviously comes from an increase of heat retention from the sun.  When the sun’s orbit is more circular and the Earth’s tilt allows the sun’s rays to strike the Earth in the North and South more directly and precession favours warmer summers, [not so effective when the Earth’s orbit is nearly circular] then ice in polar areas will melt.  It just so happens that CO2 and temperatures are low during an ice age.  It is probable that as insolation increases oceans become warmer and thus expel some of the accumulated CO2 into the air.  If the high insolation persists, then you get the combination of insolation and the greenhouse effect working together as positive feedbacks.  From the graphs, it appears that these positive feedbacks gain momentum and cause an interglacial period in a couple of thousand years or so.  There doesn,t appear to be any other factor than a temperature increase that would cause a rise in CO2.  Ice core data may not be precise enough to prove which one occurred first.  

 “Right off the bat, a most surprising conclusion in this paper is that the authors claim that correlation proves cause. Simply showing that CO2 correlates with anything surely doesn’t prove that CO2 was the cause. It’s the same kind of mindset involved with the oft-heard claim that if we have had global warming while CO2 was rising that proves the cause was the rise in CO2.”  Don J. Easterbrook, Phd