Caldeira Lab Research:Ocean acidification and ocean carbon cycle/Climate Intervention ('Geoengineering')

Sensitivity of ocean acidification to geoengineered climate stabilization

H. Damon Matthews, Long Cao, & Ken Caldeira

The use of climate engineering, large scale intentional climate modifications, is a proposed way to combat the effects of climate change. The effects that such geoengineering would have on ocean pH as well as aragonite saturation are studied here. The study revealed little to no change to pH, as well as the possible acceleration of decreased aragonite saturation.

Matthews, D.L., L. Cao,and K. Caldeira. 2009. Sensitivity of ocean acidification to geoengineered climate stabilization. Geophysical Research Letters,. 36, L10706, doi:10.1029/2009GL037488/

The effects of geoengineering on mineral saturation and pH: Average surface air temperature, pH, and aragonite saturation are shown in the pre industrial period (PI, top), in a model with predicted continuing fossil fuel emissions without climate engineering (A2, middle), and in a model with the same fossil fuel emissions but including the implementation of engineering (A2 + eng, bottom). Geoengineering greatly reduced modeled temperature but had little effect on pH or mineral saturation.

Graphical representation of the effects of climate engineering: Blue lines represent an engineered climate, while black lines represent the climate allowed to continue without engineering. Again, the only effect engineering appears to have is on temperature.


Climate engineering has been proposed as a possible response to anthropogenic climate change. While climate engineering may be able to stabilize temperatures, it is generally assumed that this will not prevent continued ocean acidification. However, due to the strong coupling between climate and the carbon cycle, climate engineering could indirectly affect ocean chemistry. We used a global Earthsystem model to investigate how climate engineering may affect surface ocean pH and the degree of aragonite saturation. Climate engineering could significantly re-distribute carbon emissions among atmosphere, land and ocean reservoirs. This could slow pH decreases somewhat relative to the non-engineered case, but would not affect the level of aragonite saturation due to opposing responses of pH and aragonite saturation to temperature change. However, these effects are dependent on enhanced carbon accumulation in the land biosphere; without this, climate engineering has little effect on pH, and leads to accelerated declines in aragonite saturation.