There are two places we can store the captured CO2: deep ocean or underground.
(1) If we sequester CO2 in deep ocean, ocean acidification and oxygen depletion will inevitably endanger the ocean ecosystem. In addition, we cannot avoid leakage from the ocean carbon reservoir.
(2) If we sequester CO2 in underground, the "leakage" of the stored CO2 will impose unanticipated burdens on our offspring. Therefore, the author asserts that sequestering CO2 underground is in essence the same as storing nuclear waste under Yucca Mountain.
I think the message from this research is:
"The carbon capture and sequestration (CCS) cannot be any way to mitigate anthropogenic climate change. Burying CO2 is just another way of hiding our mess from our children."
Source: Shaffer, G. (2010). Long-term effectiveness and consequences of carbon dioxide sequestration. Nature Geoscience, doi:10.1038/ngeo896. [Full-text at http://dx.doi.org/10.1038/ngeo896]