July 30, 2008
Carbon Dioxide Increases Ocean Acidity
The CO2 that dissolves into the ocean continues to worry me more than global warming.
By absorbing carbon dioxide from the atmosphere, and from the human use of fossil fuels, the world's seas function as a giant buffer for the Earth's life support system. The chemical balance of the sea has long been regarded as immovable. Today, researchers know that the pH of the sea's surface water has gone down by 0.1, or 25 percent, just since the beginning of industrialisation just over a century ago. Jon Havenhand and Michael Thorndyke, researchers at the University of Gothenburg, along with colleagues in Australia, have studied how this acidification process affects marine animal life.
As part of the study, which is one of the world's first on this subject, they have allowed sea urchins of the species Heliocidaris erythrogramma to fertilise themselves in water where the pH has been lowered from its normal 8.1 to a pH value of 7.7. This means an environment three times as acidic, and corresponds to the change expected by the year 2100. The results are alarming.
Like most invertebrates, the sea urchin multiplies by releasing its eggs to be fertilised in the open water. However, in a more acidic marine environment, the sea urchin's ability to multiply goes down by 25 percent, as its sperm swim more slowly and move less effectively. If fertilisation is successful, their larval development is disturbed to the extent where only 75 percent of the eggs develop into healthy larvae.
In a nutshell: We have lots of ways available to cool the planet with cheap affordable climate engineering. So global warming seems reversible if it becomes a problem. But how to deacidify the ocean if high atmospheric CO2 causes lots of CO2 to dissolve into the ocean? I ask again: does anyone have an idea for a cheap way to reverse CO2-caused acidification of oceans?
We might get lucky with cheap photovoltaics that could cause the demand for coal to plummet in 10 years. Add in the coming decline off the world oil production plateau and CO2 emissions might be on the decline in 10-15 years. Then again, maybe high rates of coal burning will extend until nanobots make construction of wind farms and solar concentrator farms really really cheap. But it would be good to have a way to reverse ocean acidification.
I'm no expert on this, just remembering basic school science.
The solubility of gases in water decreases with rising temperature.
Meaning as the ocean waters warm, the sea should outgas (release CO2) into the atmosphere, and the pH should rise. According to global warming theory this increase in atmospheric CO2 should lead to even more global warming, by forming a positive feedback loop until a new equilibrium is reached. In this equilibrium the oceans pH would be relatively high, and the world warmer, good for the sea urchins and plant growth.
But why did the pH decrease then?
I suspect another environmental disaster being responsible for this: acid rain.
As we all know, volcano eruptions and burning sulfur rich coal and fossil fuels produces acid rain which ultimately acidifies the oceans.
So this would explain why the pH went down instead of up, while the ocean waters got warmer.
Another possibility is a change in the vertical temperature profile of the sea waters. Decreasing stratification would bring cool sub surface waters rich in CO2 to the surface. This would mean acidification of the surface waters and more outgassing.
How to make the oceans less acid though? Stop burning sulfur rich fuels would help for sure. Another thought of dumping lime into the oceans probably is too crazy and would be very expensive.
CO2 acidification has been shown not to be a serious threat in more real world conditions.
Also, I recently read about using lime to reduce atmospheric CO2 by burning it (releasing some CO2)and then dumping it in the oceans. It acts as a buffer, reducing ocean CO2 concentrations and allowing more CO2 to be absorbed from the atmosphere.
Well, we know that there have been times in the past when there were much higher levels of CO2 in the atmosphere than now, so I wonder if there isn't some natural process that serves to moderate the trend toward increasing acidification.
so I wonder if there isn't some natural process that serves to moderate the trend toward increasing acidification
Dissolution of calcium carbonate buffers the acidification, and will draw down atmospheric CO2 over a period of thousands of years. Reaction of acid seawater with olivine in the sea floor (particularly near mid ocean ridges) might also be important, I guess. This buffering would happen too slowly to blunt acidification in the near term, though, unless it can somehow be accelerated. The quantity of minerals needed would, of course, be very large.
Why did the sea urchins object when researchers dumped concentrated HCl and H2SO4 right on top of them? Very odd.
David A. Young,
Regarding times in the past: A few tens of millions of years ago Antarctica was free of ice. Some hundreds of millions of years ago the world was an ice ball and its ice age was probably ended by massive volcanic eruptions.
My point is that the natural controlling factors tend to let things go pretty far in various directions before forcing conditions back in some other direction. I wouldn't leave it all up to Mother Nature.
I have a hard time believing that ocean acidification will be a problem for marine invertebrates. Most of these species produce hundreds to many thousands of offspring each time they spawn, few of which reach adulthood under the best of circumstances. These are exactly the sorts of organisms that should adapt fairly easily to a changing environment. We are not talking about condors here, but something more analogous to the bugs on a farm. You can kill them pretty easily with insecticides, but if you keep using the same one year after year pretty soon they will adapt.
Disregard that first question. I see what they are saying; that it represents a 25% change in hydronium ion concentration. However, this is a horribly misleading representation of the facts. Considering that, by the same calculations brewing coffee (pH 4.9) changes the acidity of distilled water (pH 7.0) by 12,489%.
One other thing...I'm sorry that I don't have time to look it up right now but I'm fairly certain that the oceans are not warming as predicted (and as a commenter above assumed). A study funded in the early part of the decade sent probes out to check overall ocean temperature at dozens of points across the globe (using some sort of probe that dove to a specific depth not affected by daily temperatures as I recall). After 6 years of temperature records, a slight cooling of the oceans was found.
Now, I don't write this in order to convince you! You should never trust some guy in the comments section, anyway. But this should be enough information to find the details of the study online...THAT's what I'm after here.
I don't think CO2 acidification is a major concern because it has happened before on a much larger scale during ice ages.
When the planet undergoes an ice age, the level of atmospheric CO2 falls off the chart as the planet grows colder. Almost all of that solvates into the newly cold oceans. If CO2 acidification poised a major threat we should see massive die offs of marine life during the start of ice ages. We don't.
Google 'carbon cycle" and you will discover the nonsense of this. Check out the many graphics showing carbon flux estimates.
The oceans already hold something like 38,000 gigatons of dissolved CO2 with estimates varying by thousands of gigatons; we humans produce maybe 7 or 8 gigatons a year from fossil fuels. Even if all of that went directly into the ocean and not into vegetation and other carbon sinks, the effect would be unmeasurable.
CO2 contains the third and fouth most common elements in the universe, and is what you and I were made of. It is not the toxic menace that some want you to believe.
Thanks for the numbers Shannon, We also convert about one ten-thousandth the energy hitting earth from the sun
including fossil fuel combustion.
My take in this is historical. During the Roman Warm Period world temperatures were at least two to three degrees above what they are now. We know this because the Romans could grow wine grapes in York, England. It cooled off around 200 AD (causing Mongolia's plains to dry up, and forcing the Hunu to move West.) At the same time the Roman empire was weakened by declining harvests in the Western Empire (they used to get two a year); the world warmed up again around 6-700, too late to save the Empire from the Huns and the other people they sent fleeing ahead of them. The new Medieval Warm Period first led to an infestation of Danes (you know, the ones with horned helmets etc) in England and Normandy. Medieval peasants were able to get two harvests a year too, at least until a little after 1300 when temperatures collapsed and the world froze into the Little Ice Age, millions died in Europe from cold and famine, Charles II of England went ice skating on the Thames, the SE US suffered droughts because of few summer storms, the British in the Revolutionary War carted their cannons from the tip of New York to Staten Island on the ice, etc. The world began warming up again in the 19th century, and in the last (20th) century the 1930s were the warmest decade.
All of this was before massive industrialization. The Great Barrier Reef survived (it was even warmer in previous eras; I believe corals evolved under much higher acidity) as did sea urchins, which, you should remember, use r-selection rather than k-selection in reproducing (that is, they produce a lot of eggs.)
A big climate change now would wipe out more species than one 700 years ago or 1800 years ago. Why? Human population growth. Humans now leave far less habitat for wild species to live in and with continued population growth in Africa, South Asia, and some other areas this problem continues to get worse.
The Papua part of Indonesia is next up in the cross-hairs of lumber producers and palm oil plantation operators. One of the last unspoiled tropical jungles. This tropical jungle destruction could wipe out all wild orangutans.
Some scientists claim that 550 PPM C02 will wipe out all the coral reefs. Now, maybe we'll hit Peak Oil, Peak Natural Gas, and Peak Coal so soon that we won't ever reach 550 PPM CO2. But I'm concerned.
If this kind of stuff really bothers you, you ought to be backing efforts to fertilize plankton blooms. Iron powder seems to do the trick. The big objection seems to be that not all of the plankton drops to the bottom of the ocean to be sequestered forever. A lot of the plankton gets eaten by those pesky whales who then go on to breed irresponsibly.
Since India and China are building additional coal fired power plants at a rate that will make anything done in the US irrelevant to the carbon source side of the equation, increasing carbon sinks is the only possible way that anything can be done about the man made CO2 in the atmosphere (or in this case in the oceans).
I hope to high heaven we DO reach 500-550 ppm! Studies have shown that no deep ice age has occurred when the levels of CO2 have been over 500. Correlation does not mean causation but it sure makes you wonder. If some climate scientists believe CO2 is a temperature driver going up, surely they must believe it has an effect going the other way as well. During the billion years of life on this planet, life and natural processes have reduced the level of CO2 in the atmosphere to such an extent that we have been bouncing in and out of deep ice ages. AFAIC, the CO2 levels had become dangerously low. Along comes man to fix the problem by digging up the old buried carbon (which originally came from the atmosphere eons ago) and tossing it back into the sky.
I think mankind should be prepared to deal with the secondary consequences on an ad hoc basis, but I don't see anything so alarming that could justify the current panic and hysteria over the issue. Besides, according to sea level records from the past 16 ice ages, sea level has a bit more risin' to do in any case.
I'd rather deal with the threat of an ice age with satellites that would direct more light toward the Earth. I wonder what it would cost to put up enough satellites to reflect enough light to warm the planet a couple of degrees C.
Yes, directing more sun to earth to avoid ice ages is a nice idea, might even work. As for the cost, even $10 would be more than simply continuing to put CO2 into the atmosphere. My real problem is the chauvinistic notion that the levels of CO2 that we and our immediate forebears have lived with is somehow the natural and/or optimum level that should be maintained at all cost. Over the vast history of our planet no symmetry of CO2 sinks/sources is evident. In fact, the sinks outweigh the sources, which is why CO2 levels are currently so low vs the paleo record. I certainly do not advocate going back to 5000 ppm, but also am not averse to a further increase. Most vegetation seems to do better with more CO2 (depending on the presence of water, CO2 seems to make little difference under drought conditions) and nature (and humans) will adapt. I take alarming studies that say OMIGOD ALL THE CORAL WILL DIE with a huge grain of salt(water).
Now this may make me sound like I don't think there's any problem at all which is not the case. We do have to move away from carbon-based energy sources--if even for the fact we'll need to save some oil to make plastics and stuff barring nanotech solutions giving us replacements. :) I'm just saying that we can, and in fact should, tolerate higher levels of CO2 in the atmosphere than certain quarters claim should be the limit. It's going to happen anyway during the transition.
1) The chemistry here is staightforward and very well understood. The effects of CO2 emissions on oceanic chemistry are highly certain.
2) They didn't "[dump] concentrated HCl and H2SO4 right on top of [the urchins]", they bubbled in CO2 so as to replicate the real-world scenario. Did you even read the abstract?
3) Dissolution of carbonate and silaceous minerals is a negative feedback in response to rising atmospheric CO2 that can neautralize the effects of acidification, but it is far too slow to counteract these effects. It will take tens of thousands of years given natural weathering to neatralize the input of CO2 that we would put out by the end of the century under business as usual.
4) Wishful thinking that suggests that these changes in oceanic chemistry won't negatively affect organisms or ecosystems in no way disputes the experimental evidence which demonstrate that many organisms ARE negatively affected by ocean acidification within the range we will almost certainly see by the end of the century. Neither does wishful thinking counter the geologic evidence that demonstrate previous periods of significant ocean acidification (e.g., PETM, Triassic-Jurassic boundary) are coincident with widespread marine extinctions and the worldwide collapse of calcified reef ecosystems. It's happened before and things went to pot--there's every reason to think it would happen again.
5) Glacial-interglacial cycles over the last few million years have yielded far less change in oceanic chemistry than we will see over just the next few decades. Again, the chemistry is well constrained and highly certain.
6) The potential eco-engineering "fixes" aren't cheap and in fact are generally more expensive than simply reducing CO2 emissions. In addition, the effects of a rapid increase in oceanic calcium and total alkalinity that would generally be associated with such "fixes" are not well understood. We'd be looking at something of a Rube Goldberg machine.
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