The IPCC Third Assessment Report refers to adaptation as an adjustment in natural or human systems to a new or changing environment.22 Figure 2.3 shows the relationship between costs of climate change and adaptation. Adaptation reduces the costs of climate change by reducing the damage due to climate change even though it does not influence the rise in global temperature. The net benefit of adaptation persists even after the costs of adaptation are added, illustrating that adaptation is always beneficial. Adaptation programs have other such advantages, such as making society more resistant to other disasters.
Various types of adaptation can be distinguished, including anticipatory and reactive adaptation, private and public adaptation, and autonomous and planned adaptation. An array of adaptation options is available, but more extensive adaptation is required to reduce vulnerability to climate change than is occurring now. Expanding the options for adaptation also means better understanding of limits and costs.