The global warming is mainly caused by carbon dioxide (CO₂). There are measures to mitigate the global warming such as reducing the energy consumption, and expansion of CO₂ absorption resources by forests, etc. The aim of our research group is to develop the technologies to store the captured CO₂ in the subsurface and ocean as key measures to mitigate the global warming. We have primarily researched geological storage in deep saline aquifers and ocean sequestration by CO₂ dilution technology at mid-depth ocean.