ABSTRACT

Past greenhouse gas emissions have already altered the earth's climate, “locking in” some amount of additional change to temperatures, sea levels, and precipitation patterns that can no longer be avoided (see Chapter 1). Even the ambitious mitigation scenarios described in Chapter 8 that limit global mean warming to 2°C would not prevent all significant future damages (see Chapters 3 and 4). The large and diverse set of measures aimed at reducing vulnerability to these damages and enhancing resilience with regard to changing climatic conditions is collectively referred to as adaptation. AR4 reviewed the limited state of the adaptation literature as of 2007, explaining:

Adaptation occurs in physical, ecological, and human systems. It involves changes in social and environmental processes, perceptions of climate risk, practices and functions to reduce potential damages or to realize new opportunities…. In practice, adaptations tend to be on-going processes, reflecting many factors or stresses, rather than discrete measures to address climate change specifically.

(IPCC 2007a, Working Group II, Chapter 17.4)