"But it is important to say we simply don't have any evidence in this paper to suggest that any carbon coming from these seeps is entering the atmosphere."
This quote comes from Professor Adam Skarke of Mississippi State University. Context: this is an article about recent research into releases of methane from clathrates in the seabed off the American coastline. As we know, a warming ocean is highly likely to lead to a greater trend of release of methane than has hitherto been the case, because the equilibrium level of clathrate formation and melting changes with temperature. The released methane mostly is oxidised in the sea, adding a 2:1 molecular ratio of water and dissolved carbon dioxide to it.
It’s understandable that Professor Skarke would want to hedge his comments a bit. But hang on . . .
The fact that a strong solution of CO₂ is being added to the sea in this way is not unimportant:
Firstly, ocean acidification is a huge problem, perhaps greater than atmospheric global warming and consequent climate change taken as an isolated phenomenon. (Unless that becomes so extreme as to be capable of causing near-extinction of terrestrial life by itself.)
Secondly, the source of new CO₂ is irrelevant; as the sea acquires additional CO₂ it will be able to absorb less from other sources. The equilibrium levels of carbonic acid and atmospheric CO₂ will change in the same way. Leaving aside the point that it is almost impossible that some of this actual carbon will not reach the atmosphere through normal diffusion (and you’d have an uphill struggle trying to prove otherwise), eventually it makes no difference — the methane seeps might as well have been turning direct into atmospheric CO₂ — all that would do would be to encourage more of the other sources to dissolve in sea water instead. There may be a short-term difference in levels at different depths but over time the effect will even out. There is no proven effective mechanism which can actually return the additional carbon to a stable form in the critical period of the next few centuries, against the background of a general rise in atmospheric and oceanic temperatures. (It might be different in an decreasingly acidic, limestone-forming ocean, but that’s not the situation we’re facing.)
Therefore it is not important to say that we have no evidence that any of this carbon is entering the atmosphere. (Yet.) What is important is that people should grasp that one of the most basic concepts in chemistry — equilibrium — is one of the most important ecological functions which will affect our future.
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