Emissions of fossil fuel of anthropogenic origin have been increasing since the beginning of the industrial era. The excess carbon dioxide has been partially absorbed so far both by the terrestrial vegetation and by the ocean by about 2 PgC/year for each sink. The carbon dioxide entering the ocean immediately reacts with seawater forming carbonic acid (H2CO3) with consequences for the pH of oceanic waters and triggering ocean acidification. Modeling studies, projecting emissions in the future, suggest that the increase in emissions will exacerbate the problem with severe increase in the corrosiveness of seawater. These results also imply that acidification of the oceans would result into a severe threat for planktonic organisms building calcareous shells with consequences both for the marine food web and for the global carbon cycle. In this study we revisit a previous modeling study using the MIT IGSM2, an earth system model of intermediate complexity, with a 2D atmospheric and 3D seaiceocean models including an ocean carbon cycle model with an explicit representation of the biological pump. We apply two different scenarios, with and without a policydriven stabilization of emissions of fossil fuels. IGSM2 captures the trend of surface ocean acidification comparable to that estimated by a suite of ocean carbon models with a more sophisticated representation of ocean physical processes (Orr et al., 2005). In fact IGSM2 results show that by year 2100 surface ocean pH might drop by up to 0.4 units. ISGMS2 also captures the undersaturation state with respect to aragonite of the surface Antarctic Ocean by 2100. The explicit representation of the Arctic Ocean in IGSM2 shows that the process of acidification in the Arctic is larger than in the Southern Ocean by 2100 and more so by 2200. Possible mechanisms for this asymmetry are discussed in this preliminary study. We also compare the effect of emissions scenarios on pH reduction in the framework of policy making and atmospheric CO2 stabilization.