[SIZE=+1]Are oceans becoming more acidic?[/SIZE]
Measurements done during two NOAA voyages in the Pacific, about a decade apart, are the cause of the whole ruckus about ocean acidification. From these two voyages (one experiment) it is claimed that the average alkalinity of the ocean decreased by just 0.025 pH units amounting to an increase in DIC (CO2) of 15µmol/kg (0.73% of a total of 2050µmol/kg). I have not been able to ascertain whether adequate precautions have been followed, because measuring an absolute difference of 0.1pH borders on the margins of the possible, let alone 0.01. In the decade between the two voyages, also the pH measuring apparatus has changed, and so on. But a pH unit of 0.025 on a rather exponential (logarithmic scale) amounts to antilog(-0.025)=0.944 or 5.6% more hydrogen ions. Note that this is the only accurately measured value.
[SIZE=-1]1. Feely, R A (2006):Carbon dioxide and our ocean legacy in PMEL/NOAA[/SIZE]