2011-06-12 23:25:09Someone asked me to comment on what I think is a IPCC statement
Paul D



"CO2 in the atmosphere and in the ocean reach a stable balance when the oceans contain 50 times as much CO2 as the atmosphere. The IPCC postulates an atmospheric doubling of CO2, meaning that the oceans would need to receive 50 times more CO2 to obtain chemical equilibrium. This total of 51 times the present amount of carbon in atmospheric CO2 exceeds the known reserves of fossil carbon"


Anyone got an answer?

2011-06-12 23:28:06
Paul D

Actually the comment appears to be from a skeptic: Tom Segalstad    Geology Professor
Is there a rebuttal?
2011-06-12 23:52:11
Dikran Marsupial
Gavin Cawley

I don't know off-hand if the numbers are true, but it wouldn't surprise me, and AFAICS it doesn't refute anything in the mainstream position on the carbon cycle.

To get to a stable balance would require tens to hundreds of thousands of years as you would need to equilibriate CO2 in the deep ocean as well as the surface waters.  So if you wanted to produce a permanent change in atmospheric CO2 you may well need 50 times as much CO2 as you wanted to remain in the atmosphere.  But nobody is saying that the problem is a permanent increase in atmopsheric CO2.

I suspect the basis of the canard is leaving out the small fact about taking tens of thousands of years to reach that equilibrium.  What does it matter if CO2 falls back to pre-industrial levels after a few tens of thousands of years if we fundamentally screw agriculture and the environment in the next couple of centuries?

The adjustment time of CO2 is about 70-200 years, which is the time taken for (mostly) the surface oceans to mop up about half of the excess CO2.  However full adjustment will take much longer (see the work of David Archer - he has some good videos on his website).  The Earth will eventually deal with the excess CO2 over geological timescales, the Earth is fine, it is largely us that has the problem.

Basically, it may well be true, but it is a straw man or red herring.


2011-06-13 00:02:29
Dikran Marsupial
Gavin Cawley

Having has a look at the article, you might want to looks at the SKS articles concerned with "residence time".  Segalstad doesn't understand that there is a difference between residence time and adjustment time.  The first is the length of time an individual molecule of CO2 stays in the atmosphere, the latter is the length of time it takes for an excess of CO2 to be taken up by the surface ocean.  The two are not the same because there are vast exchanges of CO2 between the atmosphere and surface oceans and terrestrial biosphere each year, which mean that about a fifth of the CO2 in the atmosphere is taken up each year.  However this is balanced by emissions from the surface oceans and terrestrial biosphere, so it means the residence time is short, but it doesn't affect the adjustment time as an exchange of CO2 between reservoirs doesn't change the level of CO2 in the atmosphere.  This is pretty much carbon cycle 101 and the fact that Segalstad and Solomon don't understand it says it all really.

That is what they are talking about when they say that people used to think that CO2 couldn't stay in the atmosphere more than 5-10 years and that this was proven by isotopic studies.  That is a statement about residence time, not adjustement time and hence is irrelevant.

There is little excuse for this, the IPCC reports clearly explain the difference between residence time and adjustment time. 

2011-06-13 00:04:55
Paul D


Thanks Dikran.

2011-06-13 00:07:18
Dikran Marsupial
Gavin Cawley

BTW I suspect the claim that Segalstad was an expert reviewer for the IPCC just means that he submitted comments on the drafts when they were released for anyone in the world to comment on them if they so chose (i.e. it means precisely nothing).  By that logic, I could have been an IPCC expert reviewer if I had contacted them to say the cover should have the words "don't panic!" written on it in large friendly letters ;o)

2011-06-13 00:56:14


Henry's Law:


at T = 25 C,

partial pressure of CO2 = k * Concentration of CO2 in water

where k = 29.41 (atm)/(mol/L)

If we divide both sides by Po = 1 atm:

fraction of CO2 = 29.41* (Co)/(mol/L)

So 150 years ago, the fraction of CO2 was 280 ppm = 2.8e-4, so the concentration in water was

Co = (2.8e-4)/29.41 (mol/L) = 9.52e-6 (mol/L)

There is about 1021 L of water, so in principle the oceans would have held about 1012 mol of CO2 in the pre-industrial era; an increase of 35% would be 3.5e11 mol of CO2, corresponding to 3.5e11 * 12 (gm) = 4.2e13 (gm) of Carbon.

If commercial coal is 80% Carbon by weight, this corresponds to 4.2e13/0.8 = 5.25e13 (gm) coal = 5.25e10 (kg) coal

Estimating world proven reserves of coal at 930 billion short tons = 8.44e14 (kg)

World Reserves of Coal/(amount of coal needed to complement the 35% CO2 concentration increase) = 16,000.

So, by my estimate, we have 16,000 times as much coal as needed to match our current 35% increase in CO2.

So, I think he's dead wrong: we could double the CO2 content about 14 times with the coal we have.

This calculation is very rough, and needs to be done more carefully to take into account the fact that the partial pressure is linear in the amount of CO2, but the % is not quite. On the other hand, a counterbalancing point is that the calculation assumes that the CO2 in the oceans is well-mixed; this is not really true, so the CO2 concentration of the atmosphere can grow quite a bit faster that this calculation would indicate.

Someone who's better with chemistry than I should do this more carefully.

2011-06-13 02:22:30
Paul D


Hopefully I won't have to take it further. The person left the comment as an off topic subject to the article.

2011-06-13 02:24:23
Paul D


Maybe this is worth a posting/rebuttal on?