SoftestPawn’s Weblog

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CO2 Emissions vs Atmospheric Change

Posted by softestpawn on March 1, 2009

A good argument for man made fossil fuel-burning global warming is along the lines of the good match between CO2 emissions and atmospheric CO2 increase. If we release 5Gt of carbon in CO2 into the atmosphere, and the amount in the atmosphere increases by 5Gt, it would be a bit churlish to insist it’s only a coincidence.

So let’s have a quick look and see if this match exists, by comparing emissions with atmospheric change in gigatons of carbon. Atmospheric CO2 is from Mauna Loa and the Law Dome proxies, and is given in ppm (parts per million). CDIAC give 1 ppmv of CO2= 2.13 Gt of carbon. Human CO2 emissions are from CDIAC, I think here (they’ve moved their pages).

Which gives us this (click to enlarge):


So we have a fairly long period where CO2 levels increased faster than emissions, a ‘cross over’ around the early 20th century where emissions do actually match (ish) atmospheric increase. Then the curious 1935 collapse (ie before WW2), where CO2 increase slowed and in fact CO2 levels dropped, despite annual human CO2 emissions of over a gigaton a year.

The last rise since the war actually tails off – the increases are slowing according to a 2d polynomial fit – rather than rapidly increasing as CO2 emissions have.

The last 15 years look particularly ‘broken’.

Now of course there are other carbon sources and sinks that vary over time. Which is rather the point; assuming there is some kind of ‘equilibrium’ that humans are disturbing is to take an oversimplistic view of ‘nature’.

(Spreadsheet is available here)


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