Abstract

From the Executive Summary:

Climate change resulting from increased greenhouse gas concentrations has the potential to harm societies and ecosystems. In particular, agriculture, forestry, water resources, human health, coastal settlements, and natural ecosystems will need to adapt to a changing climate or face diminished functions. Reductions in emissions of greenhouse gases and their concentration in the atmosphere will tend to reduce the degree and likelihood that significantly adverse conditions will result. Consideration of actions—e.g., mitigation policy—that can reduce this likelihood is reasonable and prudent, and has generally been the primary focus of public attention and policy efforts on climate change. However, recognition is increasing that the combination of continued increases in emissions and the inertia of the climate system means that some degree of climate change is inevitable. Even if extreme measures could be instantly taken to curtail global emissions, the momentum of the earth’s climate is such that warming cannot be completely avoided. Although essential for limiting the extent, and indeed the probability, of rapid and severe climate change, mitigation is not, and this paper argues, should not be, the only protective action in society’s arsenal of responses.

Adaptation actions and strategies present a complementary approach to mitigation. While mitigation can be viewed as reducing the likelihood of adverse conditions, adaptation can be viewed as reducing the severity of many impacts if adverse conditions prevail. That is, adaptation reduces the level of damages that might have otherwise occurred. However, adaptation is a risk-management strategy that is not free of cost nor foolproof, and the worthiness of any specific actions must therefore carefully weigh the expected value of the avoided damages against the real costs of implementing the adaptation strategy.