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Assessing risks and vulnerabilities to climate change

2.3 General sequence for climate impacts, vulnerabilities and risk assessments

Several decisions need to be taken when carrying out a climate impacts, vulnerabilities and risk assessment. Firstly, it is important to define the objective, the context and the scope of the assessment (I). Once the potential climate risks have been defined, a selection and prioritization of risks should be made (II). For each selected risk, additional data and information should be acquired (III) and a specific risk assessment should be carried out (IV). Finally, overarching risks and risk hot spots should be identified (V).

I. Define objectives, context and scope of the climate impacts, vulnerabilities and risk assessment

Each impacts, vulnerabilities and risk assessment should match with the overall objectives of the adaptation planning process which have been set before (see Step 1). The following questions may help to fine-tune a CCIV assessment:

  • On which impact, vulnerability and risks should the assessment focus (e.g. only on risks related to certain hazards of for specific sectors)?
  • What is the temporal reference? It is recommended to always include the current situation as a baseline. For future climate risks at least one time period which is inside a typical adaptation time range is recommended, e.g. in 2050 (30 years from now).
  • Which methodology should be applied? Depending on the objective, scope and available resources, the assessment method must be decided. An in-depth CCIV assessment which is based on climate (impact) data and simulations can easily take one or two years. Often, good results and indications for adaptation planning could already be achieved with more participatory, qualitative approaches.
  • Who should be involved? Ideally involve the same stakeholders (experts, decision makers) as in the adaptation planning process to allow a smooth transition from the CCIV assessment to the identification of adaptation measures.

A result of this activity is usually a definition of the system of concern (e.g. climate risks for agriculture and forestry in a specific district) and a preliminary list of potential climate risks which could be relevant for the assessment.

II. Prioritize and specify selected risks and develop impact chains

Since no assessment can cover all potential risks, a selection and prioritization of risks should be made based on the relevance for the selected system. Past experience and commonly available information on potential climate impacts and risks from Step 1 can be taken as a starting point.

For each selected risk it should be analysed, which climate hazards, intermediate impacts as well as vulnerability and exposure factors are leading to this specific risk and should be considered in the assessment. Impact chains can be a useful concept to guide through this step. It is helpful to organise the prioritization of risk and the development of impact chains as a participatory approach together with stakeholders. This helps to consider specific local or regional conditions, increases the acceptance of the results and facilitates the transition from risk assessment to adaptation planning.

III. Collect information on climate, hazards, exposure and vulnerability for specified risks

Based on the specified risks and impact chains, data and information on climate hazard, exposure and vulnerability should be collected. As a typical request, the assessment should provide the following information:

  • Information on past and current climate related impacts and risks. Learning from the past and present situation is crucial for identifying obvious or hidden vulnerabilities of the system. This includes data on past events and their impacts as well as trends (see Step 1.5 for data sources), but also narratives of complex interactions that are often unexpected.
  • Current climate situation and future trend projections of various climate variables and hazards (e.g. average temperature, heat days, intensive rainfall events, snow cover), based on a range of different climate scenarios, for instance Representative Concentration Pathways (RCPs) as adopted by the IPCC for its 5th Assessment Report (AR5). See Climate Impacts in Europe and Step 1.5.
  • Simulation or scenarios on future risk. For some categories of climate risks, such as water related risks or risks related to agriculture, simulation approaches exist. Future water availability or expected yield can be simulated with models taking into account different climate scenarios. However, such simulations are mostly limited to physical impacts of a hazard and do not fully consider vulnerability factors. They should therefore be interpreted as proxies of what could happen and should be complemented by further expert knowledge.
  • Data and information on exposure and vulnerability as identified for the specific risk. This includes data on current socio-economic conditions such as on population density or age structure but might also include qualitative information such as on institutional capacity to cope with a specific risk.
  • Future socio-economic development and other non-climatic factors and megatrends such as demographic change, use of resources or market trends have a significant influence on a vulnerability to climate change. While it is often difficult to get any information about potential future socio-economic development, such trends are often as important for a risk as climate change itself. For example, the future risk of heat related health problems is most likely not only increasing because the frequency and intensity of heatwaves is increased, but also because the population in cities is increasing and the population is aging.

IV. Carry out an assessment for each specific risk

There are different approaches to get from the information pool from Step III to a risk assessment for each specific risk. Most important is to understand that each risk assessment is value-based, meaning that there is no "objective risk". Risk is always assessed against agreed values or objectives. Therefore, a risk is mostly expressed in a qualitative scale such as "low, medium, high". There is even no standard definition of what a "high" risk means. The "value-setting" has to be part of the risk assessment and must be agreed upon by the stakeholders. A "high" risk could for instance be defined by a high expected damage related to the risk in the sense of economic, ecologic, functional, human health related or cultural damage.

In more data-driven, top-down and spatially explicit approaches an established method is to base the whole risk assessment on indicators. Indicators are then defined for single factors and components, which are then aggregated to composite indicators. This approach is on the one hand useful for large scale assessments with many sub-units (for instance municipalities within a district), is transparent and replicable. On the other hand, many subjective decisions on how to transform data and information into indicators and how to aggregate indicators must be taken.

For more bottom-up local risk assessments it is often more suitable to follow a participatory assessment approach based on the data and information pool from Step III. The assessment can still follow the logic of the IPCC and the impact chains by assessing hazard, vulnerability and exposure components separately. The final assessment procedure can be a consensus-based approach or a voting approach. Often, the discussion on the importance of single elements and specific vulnerabilities in a consensus-based approach opens the discussion towards adaptation options.

The result in both cases (top-down indicator based vs. bottom-up consensus bases) are:

  • a narrative description for each specific risk, including the processes and factors which lead to this risk, a description about the past and current situation, a perspective on potential future development of the single factors and the specific risk.
  • a specific evaluation for each risk (e.g. low, medium, high) for each selected time period (e.g. present situation, mid of the century, end of the century). In case of an indicator-based assessments, results could also be illustrated as risk maps. But even in a bottom-up approach, maps are useful to illustrate spatially explicit information for certain aspects of specific risks or the underlying components and factors.
  • a description about uncertainties in the assessment and the confidence level of the results (See Step 2.5).

V. Identify overarching risks and risk hot spots

The last step in each risk assessment, at least if more than one risk is assessed, should be an analysis of interactions across single risks. The main aim is to identify spatial or thematic hotspots, which are affected by more than one risk. This could for instance be urban conglomerations which are particularly affected by heat related risk but also by pluvial floods and river floods, have a high exposure (high population density) and a high vulnerability (high proportion of vulnerable people). Furthermore, some risks are linked in risk cascades. For instance, the risk of damage by landslides can lead to a risk for traffic blockage. Such risk hotspots and risk cascades can often be linked with a high adaptation demand.

In addition to risk and vulnerability, positive impacts (opportunities) can result from future climate change. Agriculture and forestry may benefit from a longer growing season, for example. Conditions are likely to be created which suit new business opportunities and innovation, and governments may respond with targeted pioneer support.