Noise versus signal
My latest Mind and Matter column in the Wall Street Journal:
Coral reefs around the world are suffering badly from overfishing and various forms of pollution. Yet many experts argue that the greatest threat to them is the acidification of the oceans from the dissolving of man-made carbon dioxide emissions.
The effect of acidification, according to J.E.N. Veron, an Australian coral scientist, will be "nothing less than catastrophic.... What were once thriving coral gardens that supported the greatest biodiversity of the marine realm will become red-black bacterial slime, and they will stay that way."
This is a common view. The Natural Resources Defense Council has called ocean acidification "the scariest environmental problem you've never heard of." Sigourney Weaver, who narrated a film about the issue, said that "the scientists are freaked out." The head of the National Oceanic and Atmospheric Administration calls it global warming's "equally evil twin."
But do the scientific data support such alarm? Last month scientists at San Diego's Scripps Institution of Oceanography and other authors published a study showing how much the pH level (measuring alkalinity versus acidity) varies naturally between parts of the ocean and at different times of the day, month and year.
"On both a monthly and annual scale, even the most stable open ocean sites see pH changes many times larger than the annual rate of acidification," say the authors of the study, adding that because good instruments to measure ocean pH have only recently been deployed, "this variation has been under-appreciated." Over coral reefs, the pH decline between dusk and dawn is almost half as much as the decrease in average pH expected over the next 100 years. The noise is greater than the signal.
Another recent study, by scientists from the U.K., Hawaii and Massachusetts, concluded that "marine and freshwater assemblages have always experienced variable pH conditions," and that "in many freshwater lakes, pH changes that are orders of magnitude greater than those projected for the 22nd-century oceans can occur over periods of hours."
This adds to other hints that the ocean-acidification problem may have been exaggerated. For a start, the ocean is alkaline and in no danger of becoming acid (despite headlines like that from Reuters in 2009: "Climate Change Turning Seas Acid"). If the average pH of the ocean drops to 7.8 from 8.1 by 2100 as predicted, it will still be well above seven, the neutral point where alkalinity becomes acidity.
The central concern is that lower pH will make it harder for corals, clams and other "calcifier" creatures to make calcium carbonate skeletons and shells. Yet this concern also may be overstated. Off Papua New Guinea and the Italian island of Ischia, where natural carbon-dioxide bubbles from volcanic vents make the sea less alkaline, and off the Yucatan, where underwater springs make seawater actually acidic, studies have shown that at least some kinds of calcifiers still thrive—at least as far down as pH 7.8.
In a recent experiment in the Mediterranean, reported in Nature Climate Change, corals and mollusks were transplanted to lower pH sites, where they proved "able to calcify and grow at even faster than normal rates when exposed to the high [carbon-dioxide] levels projected for the next 300 years." In any case, freshwater mussels thrive in Scottish rivers, where the pH is as low as five.
Laboratory experiments find that more marine creatures thrive than suffer when carbon dioxide lowers the pH level to 7.8. This is because the carbon dioxide dissolves mainly as bicarbonate, which many calcifiers use as raw material for carbonate.
Human beings have indeed placed marine ecosystems under terrible pressure, but the chief culprits are overfishing and pollution. By comparison, a very slow reduction in the alkalinity of the oceans, well within the range of natural variation, is a modest threat, and it certainly does not merit apocalyptic headlines.
Comments (15)
Read your book a few years ago and found it interesting and not too technical which a lot of scientific folks don't seem to consider for laymen such as myself. It's good that you try to donate to charity, I'm also sceptical about climate change doomsayers. If you do columns in a Wall Street Journal does that mean that you have no problem with the disproportinate wealth that Capitalism places in a just a few percent of the US population?
Hi Matt, I am a huge fan, but just to nit pick, one need to be careful when using the terms "alkaline" and "alkalinity" (as in the fourth and last paragraphs). Although the terms are somewhat related and sound similar, the alkalinity of a water is not a measure of how alkaline the water is. Rather the alkalinity of a water is a measure of to what degree it can neutralize an acid and primarily depends on the total amount of dissolved bicarbonate and carbonate ions present. As the pH of a water decreases the water becomes less alkaline (assuming its still above 7), but the alkalinity does not necessarily decrease. i.e., alkaline and alkalinity are two different things. Again, sorry to nitpick.
Mike - thanks, crikey, that's a fine distinction, that alkaline and alkalinity are different things! I stand corrected. Perhaps this is why the word "basic" is used, but in a general newspaper "basic" has too dominant another meaning to be easily used. Matt
Surely "alkalinity" is a case of terminology in need of reform!
Mark, you are begging the question (in the correct sense of assuming what needs to be proved), when you use the word 'disproportionate.'
Hi Matt
Just dropped by to say that I've just finished reading your book 'The rational optimist' and I thought it outstanding. A book I would recommend to anyone. Thank you.
On the matter of coral reefs, The one's I snorkelled over in the Caribbean, early last year all looked fine to me, without any noticeable changes from previous visits. Also the champaign reef at Diminica was thriving with fish, and corals not too far distant from the vents.
However, I think the real issue with reefs is algae, either it's absence or excess. The absence can be caused by sudden temperature changes.
Hi Matt
Just dropped by to say that I've just finished reading your book 'The rational optimist' and I thought it outstanding. A book I would recommend to anyone. Thank you.
On the matter of coral reefs, The one's I snorkelled over in the Caribbean, early last year all looked fine to me, without any noticeable changes from previous visits. Also the champaign reef at Diminica was thriving with fish, and corals not too far distant from the vents.
However, I think the real issue with reefs is algae, either it's absence or excess. The absence can be caused by sudden temperature changes.
Hi Matt
Just dropped by to say that I've just finished reading your book 'The rational optimist' and I thought it outstanding. A book I would recommend to anyone. Thank you.
On the matter of coral reefs, The one's I snorkelled over in the Caribbean, early last year all looked fine to me, without any noticeable changes from previous visits. Also the champaign reef at Diminica was thriving with fish, and corals not too far distant from the vents.
However, I think the real issue with reefs is algae, either it's absence or excess. The absence can be caused by sudden temperature changes.
Hi Matt
Just dropped by to say that I've just finished reading your book 'The rational optimist' and I thought it outstanding. A book I would recommend to anyone. Thank you.
On the matter of coral reefs, The one's I snorkelled over in the Caribbean, early last year all looked fine to me, without any noticeable changes from previous visits. Also the champaign reef at Diminica was thriving with fish, and corals not too far distant from the vents.
However, I think the real issue with reefs is algae, either it's absence or excess. The absence can be caused by sudden temperature changes.
Sorry, I think something went wrong there :-)
Matt,
Oceans are naturally buffered by seawater chemistry, sea floor sediments and sea floor volcanic rocks. Some 10,000 cubic metres of seawater circulates through the mid ocean ridges each year and seawater-rock reactions take place in the top 5 km of the oceanic crust. These reactions have been taking place for billions of years at times when the atmospheric CO2 content was far higher than now. The fact that there are fossil algal and coral reefs and shell fossils shows that the oceans were not acid at these times. Furthermore, CO2 in seawater exists as CO2, bicarbonate and carbonate and the proportion changes with pH, temperature and the partial pressure of CO2. In past times of very high atmospheric CO2, dolomite was precipitated from the oceans (in accord with expeimental data on mineral stability) thereby resulting in C02 removal from the oceans. When we run out of rocks, the oceans will become acid. Don't wait up. Experiments lowering the pH a small volume of seawater without buffers and seawater circulation are invalid as they do not duplicate nature.
Aren't the carbonistas trying to have it both ways? More carbon in the atmosphere AND more carbon in the water?
Playing devil's advocate, I'd protest against moving semi-submersible drilling rigs. These will attract corals in only a few months... then you transport them from ocean to ocean in a new version of the Columbian exchange and mix up the precious unique fauna.
(Yes of course the Columbian exchange was good for us. But was it good for dray-horses? Or mosquitos? Or llamas? Or that stuff before Japanese knotweed?)
good point about drilling rigs...
Come to think of it, not a good point about drill rigs. How often did Cpt Cook careen the Endeavour? Once, twice? And did Magellan do it at all?
The point about corals on drilling rigs was actually noted a few years ago when a rig was pulled up into a Norwegian fjord to be dismantled "ecologically" (instead of being towed to a deep trench and sunk). There were a number of quite rare corals found during the process - all of which had died by being pulled into up to the surface.