ISO 14091:2021 気候変動への適応 — 脆弱性、影響、リスク評価に関するガイドライン | ページ 7

4 Introduction to climate change risk assessment

4.1 Concept of climate change risk

Climate change risk describes the potential impact of climate change on societies, economies and the environment.

The main components for a risk assessment are (illustrated in Figure A.1):

• a) the hazard;
• b) the exposure of a given system to the hazard;
• c) the sensitivity of the system to the hazard;
• d) the (potential) climate change impact, i.e. risk without adaptation;
• e) the risk with adaptation (in the future).

Future potential climate change impacts can be modified by the adaptive capacity of a system.

Climate change impacts occur because a system is exposed to hazards (e.g. drought, flooding, heat stress). The sensitivity of the system (e.g. types of crops, land-use, age of the population) will determine the extent to which these hazards affect it. Impact is a function of both the exposure and the sensitivity of the system to hazards. The system’s adaptive capacity influences the degree to which the potential impact becomes a tangible risk. The vulnerability of the exposed system can be expressed as a combination of an organization’s sensitivity and its lack of adaptive capacity (the concepts of vulnerability and climate risk are illustrated in Figures A.2 and A.3).

4.2 Assessing climate change risk

4.2.1 Objectives

Risk assessments fulfil diverse objectives depending on the information needs of an organization, and on challenges caused by climate change. These can include the following.

• Raising awareness: Risk assessments help increase awareness of the consequences of climate change.
• Identification and prioritization of risks: Many factors contribute to a system’s sensitivity, exposure and adaptive capacity. Climate change risk assessments provide insight into these factors and this helps the organization to prioritize the risks to be addressed.
• Identification of entry points for climate change adaptation intervention: The final results and the process of risk assessment can help identify possible adaptation responses. Risk assessments can show where early action is required, e.g. to avoid locking-in future impacts and to highlight the need for development of adaptive capacity.
• Tracking changes in risk, and monitoring and evaluating adaptation: Repeating risk assessments can help to track changes over time and generate knowledge on the effectiveness of adaptation^[12].

4.2.2 Value-based judgements

Value-based judgements are necessary in climate change risk assessments. If impacts cannot be measured in the same units (e.g. monetary losses, reduced life expectancy in years), the selection of the most relevant climate change impacts involves value-based judgements. Another instance of a value-based judgement is the establishment of critical thresholds, if these cannot or can only partially be inferred from empirical evidence. For example, a threshold for critically low precipitation (say 200 mm/year) for maintaining a certain type of agriculture (e.g. fruit growing) in a given region can be set based on past experiences and agro-scientific know-how, but it also depends on judgements as to what is considered “critical”. To facilitate the interpretation and evaluation of the results of the risk assessment, it is important to be transparent about where value-based judgements have been applied^[10]. While value-based judgements cannot be avoided, fact-based approaches should be used wherever possible.

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