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Should adaptation be included in the projection?
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Should adaptation be included in the projection?

Projecting impacts of climate change depends not only on the climate and socio-economic scenarios that are selected, but also on the assumptions that are made about adaptation. It is therefore important to carefully consider whether to choose models that project potential impacts, which are those that "may occur without considering adaptation", in contrast to tools that project residual impacts, which include adaptation. One problematic aspect about potential impact assessments is that the theoretical assumption that people do not adapt is often empirically rather unlikely to be met.

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When impact models are available, it is then important to decide whether to choose methods that project potential impacts, which are those that “may occur without considering adaptation” (Parry et al., 2007: 876), in contrast to methods that project residual impacts, which include adaptation.

One problematic aspect about potential impact assessments is that the theoretical assumption that people don't adapt is often empirically rather unlikely to be met. The potential impact that “many millions more people are projected to be flooded every year due to sea-level rise by the 2080s”, reported in the AR4 WG2-SPM (IPCC 2007), for example, is rather unrealistic because this would assume that people continue to live in the coastal zone even though they experience frequent flooding or even permanent inundation (Hinkel 2011b). In such cases, adaptation should be included in the projection of impacts. See Table 2.4 for a description and some examples.

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Table 2-4: Impact-analytical methods (2).
Method Type Impact projection
Subtype Potential Impact Projection (PIP) Residual Impact Projection (RIP)
Task Project future impacts of climate change.
Characteristics of AS Interaction between the drivers and the study unit can be formally represented as a computational model. Given a scenario impacts can be computed.
Theoretical assumptions People affected do not adapt. People affected adapt.
Adaptation can be formally represented by a computational model
Steps taken
  1. Selection of climate and socio-economic scenarios
  2. Computation of the potential impacts of those scenarios
  3. Evaluation of impacts using impact indicators
  1. Selection of climate and socio-economic scenarios
  2. Selection of adaptation options and strategies
  3. Computation of the impacts of the scenarios and the adaptation strategies
  4. Evaluation of impacts using impact indicators
Results achieved A list of propositions that map each scenario to an impact. Each proposition is interpreted in the following way: "When the world evolves according to scenario e and people don't adapt, the impact on will be i". A list of propositions that map each scenario to a residual impact. Each proposition is interpreted: "When the world evolves according to scenario e and one adapts according to strategy a, the impact on the vulnerable system will be i."
Example cases Dasgupta et al. (2007) address the question of what the impacts of sea-level rise are on developing countries are. Impacts are projected for sea-level rise scenarios of 1 to 5 meter by overlaying data on land, population, agriculture, urban extent, wetlands and GDP with the inundation zones of the sealevel rise scenarios. They find that tens of millions of people will be displaced and economic damages will be severe but limited to a couple of countries. Hinkel et al. (2010) address the question of what will be both the potential and the residual impacts of sea-level rise on coastal countries of the EU27. The authors use the DIVA model to project the impacts of various sea-level rise and socio-economic scenarios on the countries first without any adaptation (potential impacts) and then with an adaptation strategy (residual impacts) that raises dikes to protect against coastal flooding and nourishes beach to protect against coastal erosion. It is found that while the potential impacts are substantial, adaptation reduces these impacts significantly by one or two orders of magnitude.
Issues involved Rarely understood that potential impacts will almost certainly not occur because adaptation will take place. E.g., people living in the coastal zone are likely to move away before experiencing permanent flooding. How to model adaptation? Model of adaptation (e.g. dumb, typical, smart and clairvoyant farmer) used has a significant indication on the results produced.

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This section is based on the UNEP PROVIA guidance document

Criteria checklist

1. You want to assess vulnerability.
2. Your focus is on impacts.
3. Either no studies on future impacts are available, or available studies are not comprehensive or credible.
4. Impact models are available that can be used to simulate future impacts.
5. As a next step you are faced with the question whether adaptation should be included in the projection.