Reconstructing Seawater pH in the South China Sea
Liu, Y., Liu, W., Peng, Z., Xiao, Y., Wei, G., Sun, W., He, J. Liu, G. and Chou, C.-L. 2009. Instability of seawater pH in the South China Sea during the mid-late Holocene: Evidence from boron isotopic composition of corals. Geochimica et Cosmochimica Acta 73: 1264-1272.
Noting that "seawater pH records that exceed a single decade are not yet available which [time period] is too short to distinguish anthropogenic and natural external forcing and fully understand natural variability of the ocean pH," Liu et al. analyzed the boron isotopic composition (δ11B) of fossil corals in an effort to reconstruct a Holocene history of sea surface pH variations for the South China Sea.
As shown in the accompanying figure, the δ11B-derived pH values for the South China Sea fluctuated between a pH of 7.91 and 8.29 during the past seven thousand years, revealing a large natural fluctuation in this parameter that is nearly four times the 0.1 pH unit decline the acidification alarmists predict should have occurred since pre-industrial times.
Given the results presented in the figure above, one cannot reject the possibility that the modern rise in atmospheric CO2 has had no effect on the pH of the South China Sea.
Caldeira, K. and Wickett, M.E. 2003. Anthropogenic carbon and ocean pH. Nature 425: 365.