what is the correlation coeefficients of greenhouse gases to temperature?

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Offline thedoc

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Wayne Hubert asked the Naked Scientists:
   Since global warming is proportional to the amount of CO2 and nitrogen oxides in the atmosphere, what is the correlation coefficients of CO2 and/or NOx to temperature??  This would show how much of the variation of these variables contribute to global warming.  We are obviously assuming there is a linear proportional relationship in all the things i have read and heard.
What do you think?
« Last Edit: 16/11/2015 19:50:01 by _system »


Offline alancalverd

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The correlation coefficients, over a long sampling period, are quite high. The problem is that correlation does not imply causation unless you can also show a positive phase relationship: that is, if A changes before B, then B cannot be the cause of A. Over geological time, it seems that temperature changes before CO2.

The same applies to short-term data. The plot of mean annual CO2 concentration versus time at Mauna Loa shows a general increase over the last 50 years, which correlates pretty well with mean annual temperature. The problem is that there is an absolutely regular seasonal variation which peaks in June every year, when anthropogenic emission is at its lowest and plants are growing most rapidly - exactly what you wouldn't expect to find. So it looks to a scientist as though temperature controls CO2, not the other way around.  And just to make it interesting, the seasonal variation at the south pole is exactly the same: CO2 maximum in December, every year.
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