Ocean Acidification: The Other CO2 Problem

by Eric Drexler on 2009/02/01

Coral reef with reflection, (cc) ST33VO, Flickr
Nice while it lasted

There’s recently been another ripple of media attention to the other CO2 problem: Not climate change, but ocean acidification. In brief: The oceans absorb a portion of CO2 emissions; this mitigates greenhouse warming, but forms carbonic acid, lowering ocean pH. Acidification of the oceans impedes the formation of coral and shells, and within decades, if trends continue, the calcium carbonate that forms the skeletons of many ocean organisms will become unstable and simply dissolve. Scientists expect that, well before that point, most coral reefs and the ecosystems they will be deeply disrupted or destroyed.

The fact that this problem exists is slowly percolating into the public mind. Understanding of a crucial aspect of the basic cause-and-effect relationship, though, has gotten approximately nowhere. This understanding is derailed by an insidious comprehension-gap, an amplified form of a comprehension-gap that derails understanding of a crucial aspect of the climate change problem.

Reducing the Rate of the Rate

CO2 emission scenarios stabilize CO2 concentrations only if the emissions fall greatly after the peak.
CO2 emission scenarios
that lead to stable atmospheric CO2 concentrations


In “Greenhouse Gases and Advanced Nanotechnology”, I described a problem at the climate-change level: Almost everyone mistakenly thinks about cause-and-effect as if CO2 were the more familiar kind of pollutant, with a pollution level is proportional to the emission rate. Instead, it is like water flowing into a bathtub with a nearly-blocked drain: Unless the flow is reduced to a trickle, the water keeps rising and the tub overflows. Short of very deep cuts, reducing emissions reduces not the CO2 concentration, but the rate of increase of the CO2 concentration. (To quote an estimated 5,000,000 web pages, “Read the FAQ”.) Likewise, capping emissions wouldn’t cap the concentration; it would cap the rate of increase of the concentration.

This is a reality that seems unlikely to make its way into widespread understanding. The comprehension gap is too large.

Now, one more level: An increment in CO2 concentration takes years to have its full effect on the acidity of surface water in the oceans, hence, on short time scale, capping CO2 emissions wouldn’t cap acidification, it would merely cap the rate of increase of the rate of increase of acidity. [9 June 09 amendment: The “short time scale” here is a bit too short. Mixing of deep and surface water is fast enough that the lag is small on the relevant time scale: For practical purposes, surface-water pH tracks CO2 concentration.]

Ocean temperatures also follow a model one integration level deeper (capping emissions = capping the rate of increase of the rate of increase of the ocean temperature), and do so more accurately, not just on short time scales. Ocean warming and cooling are slow processes of great importance to climate. A paper published this week in the Proceedings of the National Academy of Sciences (US) states that

Following [a hypothetical] cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do not drop significantly for at least 1,000 years.

The paper is titled “Irreversible climate change due to carbon dioxide emissions”.

It would be advantageous to reduce the atmospheric CO2 concentration relatively quickly. This can be accomplished only be removing it, not by capping, reducing, or eliminating emissions (nor by putting it in the sea!).

This objective could be accomplished by generating about 1021 J of electrical energy and applying it, with reasonable thermodynamic efficiency, to concentrating and removing the industrial-era anthropogenic excess CO2 from the atmosphere. This amount of energy is equivalent to about 3 TW for 10 years; current global electric power production is somewhat over 2 TW. A project like this seems unlikely to be practical until we have climbed the ladder of technologies that leads to molecular manufacturing.


Update, 9 June 09:


John Thompson February 1, 2009 at 6:45 pm UTC

And yet the former head of NASA is complaining about the “climate models” being doctored but not saying which models he refers to.

Also, the anthropogenic global warming deniers say solar cycles and long term climatology have not been explored. But from all I’ve read, solar flares and orbits and huge spans of time have been studied.

The P. R. campaign against science has got to be more specific. Guess that’s why it’s not.

Chris Phoenix February 2, 2009 at 6:45 am UTC

Biomass can be converted to charcoal instead of being allowed to decompose, which renders half the carbon non-biodegradable. If this “biochar” is then added to soil, it improves the soil in several ways.

Biochar sequestration could in theory remove about 1 PPM of atmospheric CO2 per year, while significantly improving farmland worldwide. Of course, it will take some time to ramp up to that scale. And the total carbon that can be sequestered in productive land may be limited to about 35 PPM equivalent – not quite enough to get us back to the “safe” 350 PPM, even if all CO2 emissions stopped today. But it still seems very much worth looking at.

If carbon credits can be handled properly, biochar sequestration might provide an economically sound “money pump” from developed to developing nations, on the order of $100 billion per year.

James Lovelock says this is a great idea, but it probably won’t be done. Who will prove him wrong?

Brian VanLeeuwen February 2, 2009 at 5:53 pm UTC

I don’t know why there is isn’t more concern on this issue. Certainly, I agree that the warming issue is important, but from my understanding the ocean acidification and loss of the coral reefs around the world seems to be the much more imminent effect of the rise in CO2.

Although there doesn’t seem to be a whole lot of legitimate scientific dissent that the rise in CO2 levels around to be directly caused by humans, whether the acidification problem or the warming problem will turn into the sensationalist end of the world environmental disaster scenario that the most extreme environmentalists claim they will does not seem to be as clear. From my understanding, scientists believe that there have been as many as five mass extinctions throughout the history of life on Earth where 90% of species disappear. I think that life will adapt to this sudden change as it has in the past. Of course it would be better for the human race if we could avoid this presumably extremely unpleasant scenario.

I am not convinced that pursuing nanotechnology as you originally conceived of it, Dr. Drexler, or even the modernized concept of molecular manufacturing as a primary strategy for reversing or at least halting environmental damage due to CO2 levels is the best solution. It seems like there are still a great number of rungs on the “ladder of technologies” separating us from true MNT. Wouldn’t you agree that even optimistic predictions of a time frame for development and implementation of the level of MNT required for it to be a real solution is beyond the predicted time frame of the major effects of elevated CO2 levels?

In my opinion, to ameliorate the global CO2 problem in a reasonable time frame, we need to pursue intermediate technological solutions. Research efforts across the board should be increased many fold. What we need is a “moonshot” with the focused goal of achieving true MNT. Just as with sending humans to the moon in the 60′s, a great number of auxiliary developments would be achieved along the way and those developments would help keep the CO2 levels at bay. The rapidly falling price of solar energy, for example, is promising. Once MNT is commonplace, a problem such as CO2 levels will be trivial.

Eric Drexler February 2, 2009 at 9:42 pm UTC

@Chris Phoenix

Regarding charcoal and soil, have you read 1491, a book that describes the thriving societies of the Americas in the centuries before the waves of Old-World plague that struck them down? It changed my view of history. Among other topics, the book discusses discoveries about Amazonian civilization and agriculture, and a soil-building technology employing charcoal is part of the story.

Eric Drexler February 2, 2009 at 9:51 pm UTC

@ Brian VanLeeuwen

I strongly support efforts to limit the rise in CO2 levels by more familiar means, to reduce both predicable harms and the risk of triggering unexpected feedback processes or climatic transitions.

There are many partially-effective ways to reduce harm and risk. Some are ready to apply, others are in early research. None of them can substitute for the rest. Among the purely conventional scenarios, though, even those the most optimistic look bad.

Regarding plausible timelines for developing advanced capabilities, this deserves an extended discussion. Here, I’ll just say that times short compared to those routinely discussed in the context of climate change seem entirely feasible. A rate-limiting step will be the development of a discipline centered on integrating, advancing, and applying existing technologies for atomically precise fabrication. This isn’t a matter of new technologies per se, but of suitable objectives and organization.

Erin February 13, 2009 at 3:54 am UTC

Why don’t we see more of the general public being aware of molecular manufacturing technology?

{ 1 trackback }

Previous post:

Next post: