The monitoring of carbon emissions and their removal through carbon sequestration; that is, the storage of carbon dioxide. Smith et al. (2000) Glob. Change Biol. 6 believe that energy crops have the greatest potential for carbon sequestration in Europe, and Bourque et al. (2007) Mitigation & Adapt. Stats. Glob. Change 12, 7 provide a methodology for forestry and carbon sequestration.

CO₂ may also be stored underground (see Holt et al. (1995) Energy Cons. & Manage. 36) or below the ocean thermocline. Hoffert et al. (2000) Science 298 discuss CO₂ sequestration in deep seas, and Herzog et al. (2000) Sci. Am. 282 believe that ocean injections can substantially decrease peak atmospheric CO₂ (although some CO₂ would return to the atmosphere (Kheshgi et al. (1994) Energy 19, 967). See Harvey (2003) Geophys. Res. Lett. 30, 5 on the impact of deep-ocean carbon sequestration on atmospheric CO₂. The pH impacts of ocean CO₂ disposal could be diminished by accelerating carbonate mineral weathering (Caldeira and Rau (2000) Geophys. Res. Lett. 27). Harvey (2004) Climatic Change 63, 4 warns that the impact of carbon sequestering on atmospheric CO₂ rapidly decreases over time, as there is a reduction in the rate of absorption of atmospheric CO₂ by the terrestrial biosphere and the oceans.