by ‘Guest Blogger’, December 23, 2018 in WUWT

Obiter dictum. We acknowledge that seawater is basic and cannot truly acidify (pH<7). But that is a losing semantic quibble, not a winning skeptical argument. The generally accepted linguistic convention—for better or worse–is that lowering seawater pH means ‘acidification’. There is no doubt that adding dissolved CO₂ does lower pH. The relevant questions are how much and whether that amount matters. This post answers both questions (a little, not much) without the two specific false alarms that motivated the ebook version.

There are certainly some ocean related AGW consequences beyond any scientific doubt. Henry’s Law requires that the partial pressures of atmospheric and dissolved ocean CO₂equilibrate. Rising atmospheric CO₂ must increase dissolved seawater CO₂. That is long established simple physical chemistry.

This lowers pH by increasing carbonic acid. NOAA PMEL has documented this in the central Pacific at Station Aloha off Mauna Loa where sea surface pH has declined from 8.11 to 8.07 since 1991, as dissolved pCO₂ increased from ≈325 to ≈360μatm while atmospheric CO₂ increased from about 355 to 395 ppm. That is Δ0.04 pH in 24 years.

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See also here (in French)