Monday, March 19, 2007

The Prolific Anonymous Writes:

What do you think about the de-alkalanisation of the oceans. Anything ruinously doom and gloom possible there? Is adaptation of water species quick enough by your reckoning?

It seems to me that the figure in this Wikipedia article on ocean acidification, the only evidence presented there for ocean acidification as a fact, cannot possibly be based on data. In fact, the citation is a computer simulation based on carbon dioxide transport across the air/water interface.

The vast majority of these simulations are based on incorrect physics. When I was in Sydney last year I went to a talk by a physical chemist from New Zealand who talked about how mass and heat transport are coupled: you can’t calculate the flux of carbon dioxide from water to atmosphere and vice versa just by looking at the concentrations, you need to know the relative temperatures too. I worked out his equations in Excel, and a gas will move against a pressure gradient if it is moving with a temperature gradient: i.e., if the air is hotter than the water, the concentration of carbon dioxide in the water will be higher than in the air.

This physical chemist wrote two papers on this in 1991-1992 in the climate scientists’ journal of record, Geophysical Research Letters (Phillips, Leon F.. Carbon dioxide transport at the air-sea interface: Effect of coupling of heat and matter fluxes. Geophysical Research Letters (1991), 18(7), 1221-4.; Phillips, L. F.. Carbon dioxide transport at the air-sea interface: numerical calculations for a surface renewal model with coupled fluxes. Geophysical Research Letters (1992), 19(16), 1667-70.) The papers have each been cited exactly four (4!) times. I found a paper from 2003 by a collection of climate scientist chaps from Princeton and other places, who estimated carbon uptake in various places and come to the conclusion: ‘there is more carbon dioxide uptake at low latitudes, and less at high latitudes, than the models predict.’ Well, this is because the physics in those models is wrong.

This coupling of heat and matter transport also means that there will be strong diurnal and seasonal variations in carbon dioxide transport across the air/sea interface, and local concentration of carbon dioxide very much higher than those in equilibrium with the atmospheric concentration as a whole (see some of the data in here): thus organisms in the surface water layer are regularly exposed to a pH range as great as that postulated for the 'gloom and doom' prognostications.

The Royal Society summary paper on ocean acidification does not produce any convincing evidence for an overall increase in ocean pH over the period of industrial civilisation. The 0.1 increase they cite is based on a combination of proxy data (deposits of other species correlated to pH)and simulations. I am inclined to take this value with a grain of salt (NaHCO3) and recommend that it not be used to influence policy!

3 comments:

Marco said...

I was under the impression that simulation was calculating CO2 that was being absorbed by the oceans by calculation and knowledge of the Carbon cycle. From a brief reading of the Royal Society Summary paper *they* appear convinced both of increased acidification currently, and of the future simulations of their models given different emmission assumptions. Are they being a touch mischievous and exaggerating both the certainty and magnitude of their conclusions?
Other scientists appear to be taking the tack that if the oceans do not absorb as much as these models predict, that would make the warming feedbacks all the more severe. There are also geologic ocean deposits that appear to be evidence of what happens with large sudden increases in GHG's.

Chris Fellows said...

Yes, there is a 'damned if you do, damned if you don't' quality to the ocean/air carbon dioxide balance debate. My point was that the simulations are wrong, because of their simplistic understanding of the physics of the carbon cycle.

There seems to be a strong desire out there to find a good mechanism for positive feedback to make Greenhouse warming more catastrophic- because with the core mechanism, each additional molecule of carbon dioxide should do less damage than the one before it.

I don't believe the assumption that 'carbon dioxide levels are changing faster now than they ever did in the distant past, therefore the ocean's can't possibly cope fast enough' is justified. Biological mechanisms for transfer of carbon dioxide from surface waters to deeper waters are adaptive and likely to be able to respond to changes much more rapidly than purely physical mechanisms. The thermodynamics I talked about also suggests that global warming, by warming the polar oceans, will accelerate the rate at which carbon dioxide is partitioned into the cold water (which go on to sink and carry the carbon to the depths).

I do hope the 'pet hate' you referred to over in Klaus Rohde's blog is not a reference to me. I will feel most unappreciated after you prompting me to create a science blog :(

Marco said...

No - You are the general exception to the rule here. Your scientific critiques are both scientific and unbiased. It is quite clear which of your statements are opinion, and which are in the capacity of a scientist. In fact, it is because of this pet hate that I wanted you to start this kind of blog. I was referring primarily to
1) Realclimate, whose scientists mix in statements which are their own opinion but are made to sound more authoritative because "they're the experts" and
2) The articles they often attack: Ones in an editorial or popular science setting. They read like a scientific critique, but use such biased scientific references, that it should just SCREAM "biased opinion"

I am not really sure whether, say the Royal Society Summary paper is guilty of inserting biased opinions within its paper, or whether it has motivations to do so other than a quasi-theological belief system.