Ocean CO2 uptake update

The IPCC AR4 Scientific Basis report is a real goldmine of information, even if it isn’t perfect, as I recently pointed out.

As I discussed in a previous post, an idea I later developed a little, policies to address global warming must rely on an understanding of how natural systems will respond to the increase in atmospheric CO2.  Will the oceans keep absorbing a couple of GtC worth of CO2 each year (as estimated since 1990 – AR4, p.26, as referenced previously) or more (as implicitly assumed by many) or less?  And will land ecosystems manage to take up more or less carbon than in the past?  Especially if we continue to reduce the area of ecosystems able to do this – since agricultural land clearly does not progressively store carbon.

I’ve been looking at a critical section in AR4 on ocean uptake of CO2.  This is 5.4.2.2 on p.403-5 (though the main section on the carbon cycle is 7.3, p.511 ff).  I quote:

“The fraction of net CO2 emissions taken up by the ocean (…) was possibly lower during 1980 to 2005 (37% +/- 7% [that is, 118 +/- 19 of 283 +/- 19GtC of emissions]) compared to 1750 to 1994 (42% +/- 7% [that is, 53 +/- 9 of 143 +/- 10 GtC of emissions)…  The decrease in oceanic uptake fraction would be consistent with the understanding that the ocean CO2 sink is limited by the transport rate of anthropogenic carbon from the surface to the deep ocean, and also with the nonlinearity in carbon chemistry that reduces the CO2 uptake capacity of water as its CO2 concentration increases”.  (my inserts in [ ]’s – based on Table 5.1, p.404).

And we also have to worry about “a decrease in CO2 uptake capacity” as the ocean warms.

On the other hand section 7.3.2.2.5 (p.521) notes that:

“The ocean uptake has increased by 22% between the 1980s and 1990s, but the fraction of emssions (fossil plus land use) taken up by the ocean has remained constant.”

though of course the ocean “knows” nothing about emissions – all it can possibly be affected by is the level of CO2 in the atmosphere.

We really need to get a handle on what the oceans are going to do in the future since it makes such a huge difference to the level of carbon emissions we can get away with.  It’ll be the first section I turn to in AR5.  As AR5 is due around 2012 (I suppose), maybe we should have a think about where we focus scientific resources now…

Some thoughts on sorts of science sources

OK, it’s not quite up there in the tongue-twister stakes as my best creation: “We’re wearing weird red wellies”. Try saying that quickly after a few pints!

About 10 days ago my Sunday morning was spoilt by the sight of the really rather scary, formerly reassuringly plump (maybe he’s become a vegan) ex-Chancellor of the UK Exchequer Nigel Lawson on Andrew Marr’s weekly political couch-fest. Why had he crawled out of his coffin? Well, to plug his book, of course. It is indeed one of the world’s great mysteries why the BBC is so careful not to mention products by name (to utter “Coca-Cola” without permission would be blasphemous in Beebland), yet so shamelessly allows so many people to promote their products. The occasion of Ryanair’s financial results, for example, seem to provide a free 1 minute advertising slot for Michael O’Leary. I’m surprised he doesn’t move to quarterly reporting.

Presumably, if you have good PR help, a public profile or the right connections, you can get as much time to plug a book on the BBC as you want, because, blow me down if I didn’t hear Count Lawson again on the radio a few days ago, on some type of pick of the week show on Radio 4. At least he was being grilled this time – listen and learn, Andrew Marr. But surely there should be some criteria for whether a book is worthy of BBC airtime? E.g. positive reviews by experts in the field?? Tricky, but how could anything be worse than the apparent old school tie basis of selection we have today?

Get this, Lawson’s book was turned down, he said on TV, by 7 UK publishers, but he has a “good agent” who managed to get it published overseas. Makes you wonder if it’s really worthy of promotion in the mainstream media, don’t it? I was therefore going to put TV bottom of the list of reliable science sources.

But then I read the Times’ review of Nigel Lawson’s contribution to the debate. Astonishingly, the reviewer, an Alexander Cockburn, chides Lawson for accepting the anthropogenesis of global warming! In fact, Cockburn’s review leaves me with the impression that Lawson may be saying something useful. A view dispelled by a somewhat more comprehensive (family connections?) review in the Spectator. Lawson, it seems (before I rush out to buy his work), doesn’t deny global warming, he merely downplays it, in order to argue against doing anything much at all (I’ll be more specific when I’ve read the book – which I will likely do, because, unfortunately, publicity grants de facto credibility, requiring a response). Insidious.

So, let’s award 0/10 for the informativeness of the mainstream print media (Times) and 1/10 for the broadcasters (BBC), who at least attempt to be impartial. Let’s give general current affairs (Spectator) 2/10. And let’s give published works 3/10. At least the publishers tried to stop Lawson, if to no avail; perhaps his memory of the Spycatcher affair stood him in good stead.

Now, compare this piece by Gwyn Prins from the Guardian’s Commentisfree site. For all I know, Gwyn Prins makes similar points about the ineffectiveness and counterproductivity of existing policy responses to GW as does Nigel Lawson, but at least he does not base his argument on false premises. In fact, I was interested enough to download Prins’ paper “The Wrong Trousers: Radically Rethinking Climate Policy” (written jointly with Steve Rayner). Prins & Rayner argue that GW is serious and urgent, but the Kyoto mechanism ineffective. They therefore advocate “enlightened self-interest” (ouch!). Still, a step forward from the “downplaying” strategy of a failed UK Chancellor (the Lawson Boom was followed by an inflationary bust – anyone else notice a pattern starting to develop? – let’s ignore problems until it’s too late, shall we, Nigel?).

So, let’s say 4/10 for op-ed (as the Yanks call it), and 5/10 for online publications.

But what I want to draw attention to are the exchanges in the comments on Prins’ piece. First, let’s backtrack a little. Lawson (like Nigel Calder) apparently claims the Earth is no longer warming, since annual average global temperatures have not returned to their 1998 record level. Now, as we all know, temperatures are bound to fluctuate from year to year about a long-term warming trend. All the scatter of annual mean temperatures tells us is that the annual variability of transfer of heat from the surface of the oceans exceeds the amount of heat gained by the planet each year. But, if the oceans were to cease gaining heat, without an overt cooling cause (such as a volcano) then GW theory would be in trouble – it would imply (since the oceans are so large and important in this context) that the Earth is no longer cooler than it needs to be for it to be in energy balance. Unfortunately, this is exactly what the IPCC’s 4AR implies. Yes, Fig. 5.1 on page 390 shows the oceans cooling over the last few years. Does the IPCC really explain this anomaly? No. It is “bottom-up” science – based more on observation than theory-driven.

So, say 8/10 to the IPCC. Maybe they need to put a bit more effort into the coherence of the whole package, and resolve or at least discuss these sorts of problems before rushing their 900 pages to CUP.

Anyway, I was mulling over this problemette when I noticed it discussed by PacificGatePost and deconvoluter in the comments on Prins’ Guardian piece. Phew! It turns out there was a problem with the measurements. deconvoluter refers to a Realclimate piece that gives chapter and verse.

So let’s give blogs (Commentisfree) 6/10 and specialist blogs (Realclimate) 9/10. Now we’re getting somewhere.

But there’s more. The Prins piece was in response to an article in Nature, by Roger Pielke et al arguing that the IPCC scenarios (actually I consider these unrealistic and irrelevant, but let’s put that to one side for now) are over-optimistic. The scenarios – shock!, horror! – assume some carbon “savings” will occur without specific policy to reduce emissions (um, anyone seen the price of oil today?). Now, even though the Pielke article and a Nature editorial are accessible on the internet, much of their content is subscriber only, so it does rather perturb me that so much debate (rather than actual science) is being conducted (in Scienglish) in the pages of Science and Nature. Not their fault, but what are the mainstream media doing? I believe as many people as possible need to develop their own understanding of the science and the issues. “Trust me, I’m a scientist” is only going to get us so far.

So, 7/10 in our informativeness competition to science magazines.

I gave the Realclimate site 9/10 – for trying to bridge the gap between the scientific world and normal people – but they’re not the real winner. 10/10, and the top prize goes to – yes, you’ve guessed it! – the internet itself which has made all this possible. Without it, I suggest the GW debate would be years behind even where it is now.

Confused by carbonates

Somebody please help!

I’m having great difficulty reconciling two things that I’ve read:

1. There is a carbonate “saturation horizon” at a specific depth in the oceans. Below this depth carbonates dissolve because of the high pressure. (The “saturation horizon” depth is also less where it is colder).

What’s going on is that there is a chemical equilibrium:

Ca²⁺ + HCO₃^– <–> CaCO₃ + H⁺

Adding CO₂ to the oceans – a result of adding it to the atmosphere – makes the problem worse. It acidifies the water, driving this equilibrium to the left, in effect dissolving carbonates, such as the shells of marine organisms. (The big danger is that this process will raise the carbonate saturate horizon to the surface in the polar oceans, leading to a sudden increase in acidity in the absence of the carbonate buffer, which will reduce the ability of the ocean to absorb carbon dioxide, as well as prevent organisms from making carbonate exoskeletons).

2. There is a plan afoot to dump carbon dioxide underground, in gas and oil fields and in saline aquifers (“carbon capture and sequestration” or CCS). There was an interesting article on this by Fred Pearce in last week’s New Scientist (subscriber’s only, I’m afraid). Now, said Fred, “… the chemical reactions might gradually convert the CO₂ into carbonate rock…”. But Fred also mentions the Frio project when the CO₂ “…acidified the brine allowing it to dissolve metal-oxide minerals in the rock…” which “…might eventually create tunnels in the cap rock through which CO₂ might escape”.

My question is, why wouldn’t the CO₂ in general form an acid (I assume there’s plenty of water about) and dissolve the rock? In particular, how could it form carbonate rock, when, as we see in the oceans, CO₂ in solution forms an acid which dissolves carbonate rock – more effectively at pressure? Surely this could only happen once all the CO₂ had been converted to some intermediate form? – since otherwise any remaining CO₂ would form acid and dissolve the carbonate. Can we therefore always rely on the sequestered CO₂ staying where it’s put?

Of course, I’ve consulted “Sustainable Fossil Fuels” by Mark Jaccard who notes that: “… the CO₂ may eventually either dissolve into the aquifer water (hydrodynamic trapping) or precipitate as a solid carbonate mineral by reacting with the surrounding rock (mineral trapping).” OK…

When I look at the IPCC Special Report on CCS, I see they go into all this in more detail, of course. I guess I’m happy with the chemistry – on its own – and I’m happy with the mechanics – permeability, cap-rocks etc. – on its own. It’s the interaction between the chemistry and the physics of the rock formations that bothers me. The IPCC notes that:

“Reaction of the dissolved CO₂ with minerals can be rapid (days) in the case of some carbonate minerals…” (section 5.2.2.3, p.209).

and that:

“Reaction of the CO₂ with formation water and rocks may result in reaction products that affect the porosity of the rock and the flow of solution through the pores. This possibility has not, however, been observed experimentally and its possible effects cannot be quantified.” (section 5.2.2, p.210).

Perhaps we’d better quantify it before we get our hopes for CCS up too high. What was the Frio project if it wasn’t an experiment? Puzzlingly, the IPCC report only mentions the Frio project as 1600tCO₂ “pilot” (Table 5.1, p.201) and one of several that:

“…demonstrate that subsurface injection of CO₂ is not for the distant future, but is being implemented now for environmental and/or commercial reasons.” (section 5.1.2, p.204).

What is this? A scientific evaluation or a sales brochure?

In general, is the approach being adopted to evaluating CCS one of identifying all the problems so that we can avoid them when we roll-out the technology, or one of trying to show that there are no problems, so that we can carry on planning to burn fossil-fuels (and building coal-fired power-stations) with as few qualms as possible?

One other annoying fact: liquid CO₂ is less dense than water, so if there is enough pressure and the reservoir is not sealed, it’s the CO₂ that will leak out, not the H₂O.

Any comments that might help allay my fears are more than welcome.