Day by Day

Tuesday, May 29, 2012

Ocean Acidity Scare Debunked


A writer to our Gualala weekly newspaper noted (Oyster evidence, ICO, May 11, 2012) that acidity of the oceans are increasing “at a rate in the last 100 years that is 10 times faster than any 100-year span in the last 300 million years.” This is interesting on many levels, most conspicuously because it’s not true. An obvious fault is that ocean pH changes cannot be measured in precise 100-year increments covering the past 300 million years.  However, there’s more.

A 2005 study (Pelejero et al.) spanning the period 1708-1988 found a clear interdecadal oscillation of pH between 7.9 and 8.2 pH units. The study showed many oscillations of 0.2 pH units within the three 100-year periods examined.

A 2009 study (Liu et al.) of the pH history of the South China Sea covering the past 7,000 years shows oscillations of 0.4 pH units, some of which decreased 0.2 pH units in a 100-year period.  About recent increases in ocean acidity, this study concluded: “(T)here is nothing unusual, unnatural or unprecedented about the two most recent pH values. They are neither the lowest of the record, nor is the decline rate that led to them the greatest of the record.”

It’s hard for a statement about acidity increasing “faster than any 100-year span in the last 300 million years” to be true when the rate isn’t the even the fastest in the last 300 years, as one study shows, or in the last 7,000 years per another study.

A 2009 Australian study (Wei et al.) found a decrease in pH of 0.4 units 1935-1940, and an earlier decrease of 0.3 units 1860-1865. Both of these reductions, as all of the previous examples, were obviously not caused by increased atmospheric CO2. It is also obvious that Oregon oysters survived them all, and should persevere.

(The writer sent another letter to our weekly newspaper that basically repeated his first letter without the slightest indication that he had read my refutation above)

According to him, a Columbia University study found we had increased the ocean’s acidity, in his words, “10 times faster than any time in the last 300 million years,” but that’s not what it says. Its headline is “Ocean Acidification Rate May Be Unprecedented,” and the report findings are qualified with the word “may” throughout.

The pH change in question is only a decrease from 8.2 to 8.1 in 200 years. To put this in perspective, a 2011 study, Hofmann, et al., High-Frequency Dynamics of Ocean pH: A Multi-Ecosystem Comparison, found many non-open ocean sites where pH varied by up to 1.4 units in a month. In the more stable and vast open ocean, Hofmann wrote: “Open-water areas (in the Southern Ocean) experience a strong seasonal shift in seawater pH (~0.3–0.5 units) between austral summer and winter.”

A Mediterranean experiment found that corals and mollusks transplanted to lower pH sites were “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.” That’s not surprising, since corals and shellfish evolved with CO2 levels 10-20 times higher than present.

Contradicting the Oregon State oyster study he cited, a 2012 Parker et al. study of Sydney rock oysters found that "larvae spawned from adults exposed to elevated CO2 were larger and developed faster" than those from nearby ambient seawater. This study exposed the flaw in the Oregon study that only considered the impacts on larvae, ignoring the carry-over effects passed from adult to offspring.

A 2012 Armin et al. study of cold-water coral found it acclimated quickly and appeared to increase growth under lower pH levels. Again, science robustly debunks ocean acidification fears and alarmism.

We have nothing to fear but Al Gore himself.


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