  In 2005, the Royal Society published a report titled "Ocean acidification due
to increasing atmospheric carbon dioxide". The report's principal
conclusion-that average ocean pH could decrease by 0.5 units by 2100-is
demonstrated here to be consistent with a linear extrapolation of very limited
data. It is also shown that current understanding of ocean mixing, and of the
relationship between pH and atmospheric carbon dioxide concentration, cannot
justify such an extrapolation.
