Comment on “Modern-age buildup of CO2 and its effects on seawater acidity and salinity” by Hugo A. Loáiciga

Caldeira, K. and Archer, D. and Barry, J. P. and Bellerby, R. G. J. and Brewer, P. G. and Cao, L. and Dickson, A. and Dony, S. G. and Elderfield, H. C. and Fabry, V. J. and Feely, R. A. and Gattuso, J-P and Haugan, P. M. and Hoegh-Guldberg, O. and Jain, A. K. and Kleypas, J. A and Langdon, C. and Orr, J. C. and Ridgewell, A. and Sabine, C. L. and Seibel, B. A. and Shirayama, Y. and Turley, C. and Watson, A. J. and Zeebe, R. E. (2007) Comment on “Modern-age buildup of CO2 and its effects on seawater acidity and salinity” by Hugo A. Loáiciga. Geophysical Research Letters, 34 (18). L18608. ISSN 0094-8276 DOI

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Official URL: doi:10.1029/2006GL027288


A doubling of present atmospheric CO2 concentrations (to 760 ppm) may occur by the end of this century in the absence of efforts to diminish CO2 emissions from fossil-fuel combustion [Intergovernmental Panel on Climate Change (IPCC), 2001]. Based on inappropriate assumptions and erroneous thermodynamic calculations, Loa´ iciga [2006] mistakenly reports that atmospheric CO2 concentrations of 760 ppm will lower the pH of the surface ocean by 0.28 relative to the natural ‘‘mid 18th century’’ conditions. He implies that a drop of this magnitude will have minimal biological impact, neglecting numerous recent experiments and observations showing that this decrease in pH would substantially affect the physiology and health of marine organisms. Here, we focus on two fundamental flaws in the published analysis that invalidate his conclusions: (1) he assumes instantaneous chemical equilibration of the ocean with carbonate minerals although this process is known to take five to ten thousand years and (2) contrary to what is implied by Loa´iciga, many marine organisms are sensitive to a pH decrease of 0.2 units.

Item Type: Article
Uncontrolled Keywords: 2007 AREP IA55 2007 P
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Geophysical Research Letters
Volume: 34
Page Range: L18608
Identification Number:
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:02
Last Modified: 23 Jul 2013 10:06

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