Vulnerability refers to the degree to which people or the things they value are susceptible to, or are unable to cope with, the adverse impacts of climate change. Thus, vulnerability determines how severe the impacts of climate change might be.
There are three dimensions of vulnerability to climate change: exposure, sensitivity, and adaptive capacity.
- Exposure is the degree to which people and the things they value could be exposed to climate variation or change;
- sensitivity is the degree to which they could be harmed by that exposure; and
- adaptive capacity is the degree to which they could mitigate the potential for harm by taking action to reduce exposure or sensitivity.
The expression “things they value” not only refers to economic value and wealth, but also to places and to cultural, spiritual, and personal values. In addition, this expression refers to critical physical and social infrastructure, including such physical infrastructure as police, emergency, and health services buildings, communication and transportation networks, public utilities, and schools and daycare centers, and such social infrastructure as extended families, neighborhood watch groups, fraternal organizations, and more. The expression even refers to such factors as economic growth rates and economic vitality. People value some places and things for intrinsic reasons and some because they need them to function successfully in our society.
Some people and the things they value can be highly vulnerable to low-impact climate changes because of high sensitivity or low adaptive capacity, while others can have little vulnerability to even high-impact climate changes because of insensitivity or high adaptive capacity. Climate change will result in highly variable impact patterns because of these variations in vulnerability in time and space.
Focus first on the difference between adaptive capacity in these two scales.
- On the left, adaptive capacity outweighs both sensitivity and exposure, thereby resulting in lower vulnerability.
- On the right, sensitivity and exposure outweigh adaptive capacity, leading to increased vulnerability.
The concept of resilience is important to understanding adaptive capacity to climate change. Resilience refers to the ability of a human system (such as a municipal water system and the community that supports it) to withstand contemporary shocks and to anticipate and plan for future shocks. Resilient systems have the ability to learn from past experiences and to use that knowledge when confronting problems. Systems with high adaptive capacity are therefore resilient and able to reconfigure themselves to deal with climate change. Systems with low adaptive capacity are much less resilient and much more vulnerable to climate change.