An approach based on sequential decision making recognises that, over time, decisions related to climate change can be revised in the light of improved information. This is particularly important with respect to climate change, due to the long-term nature of the problem. A near-term hedging strategy concerned with reducing future climate impacts might favour stringent, near-term emissions reductions. As stated earlier, carbon dioxide accumulates in the atmosphere, and to stabilize the atmospheric concentration of , emissions would need to be drastically reduced from their present level (refer to diagram opposite). Stringent near-term emissions reductions allow for greater future flexibility with regard to a low stabilization target, e.g., 450 parts-per-million (ppm) . To put it differently, stringent near-term emissions abatement can be seen as having an option value in allowing for lower, long-term stabilization targets. This option may be lost if near-term emissions abatement is less stringent.