Wrong again, huh?
Hot Topic, in a post endearingly headed “I’ve been wrong before“, berates the CCG for reporting a criticism of the Royal Society. Chemist Dr Klaus L. E. Kaiser published evidence of miscalculations by the RS which was supported by Swedish Professor of Applied Mathematics, Claes Johnson.
But unfortunately the confidence shown by Gareth Renowden in rebutting this criticism of the Royal Society does not extend to admitting the extent of uncertainty about the carbon dioxide cycle. To listen to Gareth, you’d think the science was settled, but in fact there are substantial unknowns.
He introduces his rebuttal (ignoring his opening paragraph, which contains ad hominem remarks) with this:
Unfortunately for Kaiser and Sullivan, the Royal Society (otherwise known as the most august of scientific institutions, 350 years old this year) didn’t make any schoolboy errors. The amount of CO2 in the atmosphere is determined by the interchange of carbon between the atmosphere, oceans and biosphere. Over the last few hundred years the ocean and biosphere have been doing us a big favour by absorbing two thirds of the CO2 we’ve emitted. The balance has been steadily accumulating, which is why atmospheric CO2 has risen from 280 ppm to 390 ppm.
This seems to be true, although the proportion of human emissions being absorbed by natural processes is specified variously, by different authorities, between about 45% and the 66% Gareth mentions. But whatever figure you take, it does leave a “balance” of an amount which “steadily accumulates”, accounting for a rise in atmospheric concentration from about 280 ppmv to about 390 ppmv now.
But watch the pea under the cup.
What is not mentioned is the strange matter of the increasing disappearance of CO2. Simply stated, as human emissions of CO2 have risen, so has the proportion of those emissions absorbed by nature. It seems to remain fairly constant at about 45%.
In other words, no matter (so far) how much we produce, nature is happy to take about half of it. Nobody knows (so far as I have found) how nature manages to keep increasing its absorption of our emissions. But why does nobody talk about it? Perhaps people don’t want to acknowledge just how flexible nature is. Or how little they know of nature.
Live long and prosper in a short life
Another unstated element is the contribution to increased atmospheric levels made by the out-gassing of CO2 from the oceans as they warm. I have seen no calculations of this contribution, and yet, if the water is warming, CO2 will be bubbling out of it. Only a small amount of that CO2, of course, forms part of the anthropogenic emissions budget, yet nowhere have I seen a deduction from the human sources for this out-gassing. The out-gassing also reduces the extent of ocean “acidification” but, again, nobody mentions it.
Gareth then refers us to an article at Sceptical Science describing how, yes, CO2’s atmospheric lifetime is short (five years), but it doesn’t matter because the extra CO2 stays around for centuries. If you can resolve those two competing notions, you’re doing rather well. I felt sceptical and looked for an explanation.
In what appears the thrust of his argument, the author, one Doug Mackie, states:
It is true that an individual molecule of CO2 has a short residence time in the atmosphere. However, in most cases when a molecule of CO2 leaves the atmosphere it is simply swapping places with one in the ocean. Thus, the warming potential of CO2 has very little to do with the residence time of CO2.
Well, how convenient. In such a swift and expeditious manner, therefore, it is explained that we can look forward to an eternity of CO2, whose level never falls, and rises only when a man-made molecule enters the atmosphere. This is surely nonsense. What is the evidence for “in most cases” CO2 molecules are simply swapping places with those in the sea? Why not on land? Why should the oceanic molecules differ in class or quality from those of forests and soils?
Mackie at odds with Royal Society
Considering that each year at least 45% of human emissions are absorbed somewhere, that means about half the new CO2 molecules are not “simply swapping places” with others. Yet Mackie says that “most” of them are. This is sloppy and obscure. Where does his information come from?
Please note how Mackie denies by orders of magnitude the Royal Society’s (long) view of the residence time. Anyone going to criticise him for that? But I agree with Mackie in this: “the warming potential of CO2 has very little to do with the residence time of CO2.”
Gareth now cites Real Climate. A five-year-old article by David Archer talks about the atmospheric lifetime of CO2. The heart of his argument seems to be here:
When you release a slug of new CO2 into the atmosphere, dissolution in the ocean gets rid of about three quarters of it, more or less, depending on how much is released. The rest has to await neutralization by reaction with CaCO3 or igneous rocks on land and in the ocean [2-6]. These rock reactions also restore the pH of the ocean from the CO2 acid spike. My model indicates that about 7% of carbon released today will still be in the atmosphere in 100,000 years [7]. I calculate a mean lifetime, from the sum of all the processes, of about 30,000 years.
So this is really helpful — Archer says he has a computer model. His model makes outlandish claims. Without detailing its calculations, he just enlightens us with its output: 7% of carbon remains after 100,000 years; a mean lifetime of about 30,000 years. Thanks, David. How do you know that three quarters of any new “slug” of CO2 dissolves in the ocean? Why do you ignore all terrestrial sinks? What’s in your model? Why does it disagree with 98% of published estimates?
But the rest of the article is erudite, and reaffirms the CO2-is-here-for-eternity conclusion already stated. There’s an “oops”, though: nowhere does he relate this long lifetime to some kind of sensitivity factor for raising the global temperature. In other words, what of the long endurance? What effect will it have on temperature?
It’s very hard to believe that temperature will continue rising (at least, detectably) because of present levels of CO2. Why? Simply because the temperature response to increased CO2 is more or less logarithmic. Like this:
You see, it’s the level of CO2 that determines the temperature forcing, not how long it stays there. Because a certain number of CO2 molecules will cause a measured amount of re-radiation, slowing the rate at which the outgoing IR reaches space. Remaining longer in the atmosphere won’t slow the heat transfer any further. You’ve got to add more molecules, like adding more paint to the window glass, to further slow the transfer and thus increase the temperature.
Put it another way: imagine that the present level of carbon dioxide in the atmosphere remained as it is for the next million years, neither rising nor falling. Cycling through the natural sources and sinks, certainly, but otherwise unchanging. In other words, human emissions stop now. Would you expect the temperature to rise, just because the amount of CO2 does not go down? I certainly wouldn’t, yet that appears to be what Archer is telling us.
The next graph, also from MODTRANS data, takes the CO2 levels higher so we can see what forcing increase to expect from doubling the present 400 ppmv to 800 ppmv — and we find maybe 3 W/m2. Doubling would take, I seem to remember, on the order of 60 to 80 years. And it’s a very small increase in forcing. Would it be obliterated by the tropical thermostat effect described by Spencer?
To recap, the Royal Society proposes an atmospheric lifetime for carbon dioxide of 100 years. That is, compared with over thirty scientific papers, literally an outlier. This chart shows them all:
The best argument against a runaway temperature increase remains our history: It’s never happened before, not even with atmospheric CO2 levels 17 times higher than now.
It’s precisely because of these and other uncertainties that NASA’s Orbiting Carbon Observatory satellite is endeavouring to measure the terrestrial carbon sinks from orbit.
I note that Scott Denning claims about 30% for the ocean sink. That’s a long way from the 75% Real Climate claims.
In the Royal Society position paper on climate change that prompted Kaiser’s allegation of miscalculation which we reported, they say (emphasis added):
about half of the CO2 emitted by human activity since the industrial revolution has remained in the atmosphere. The remainder has been taken up by the oceans, soils and plants although the exact amount going to each of these individually is less well known.
There’s hardly an iota of settled science in sight.
