2.3.1 Thresholds and criteria for risk
The risks of climate change for a given exposure unit can be defined by criteria that link climate impacts to potential outcomes. This allows a risk to be analysed and management options to be evaluated, prioritised, and implemented. Criteria are usually specified using thresholds that denote some limit of tolerable risk. A threshold marks the point where stress on an exposed system or activity, if exceeded, results in a non-linear response in that system or activity. Two types of thresholds are used in assessing change (Kenny et al., 2000; Jones 2001; see also Chapter 19, Section 184.108.40.206):
1. a non-linear change in state, where a system shifts from one identifiable set of conditions to another (systemic threshold);
2. a level of change in condition, measured on a linear scale, regarded as 'unacceptable' and inviting some form of response (impact threshold).
Thresholds used to assess risk are commonly value-laden, or normative. A systemic threshold can often be objectively measured; for example, a range of estimates of global mean warming is reported in Meehl et al. (2007) defining the point at which irreversible melting of the Greenland Ice Sheet would commence. If a policy aim were to avoid its loss, selecting from the given range a critical level of warming that is not to be exceeded would require a value judgement. In the case of an impact threshold, the response is the non-linear aspect; for example, a management threshold (Kenny et al., 2000). Exceeding a management threshold will result in a change of legal, regulatory, economic, or cultural behaviour. Hence, both cases introduce critical thresholds (IPCC, 1994; Parry et al., 1996; Pittock and Jones, 2000), where criticality exceeds, in risk-assessment terms, the level of tolerable risk. Critical thresholds are used to define the coping range (see Section 2.3.3).
Thresholds derived with stakeholders avoid the pitfall of researchers ascribing their own values to an assessment (Kenny et al., 2000; Pittock and Jones, 2000; Conde and Lonsdale, 2005). Stakeholders thus become responsible for the management of the uncertainties associated with that threshold through ownership of the assessment process and its outcomes (Jones, 2001). The probability of threshold exceedance is being used in risk analyses (Jones, 2001, 2004) on local and global scales. For example, probabilities of critical thresholds for coral bleaching and mortality for sites in the Great Barrier Reef as a function of global warming show that catastrophic bleaching will occur biennially with a warming of about 2°C (Jones, 2004). Further examples are given in Section 2.4.8. At a global scale, the risk of exceeding critical thresholds has been estimated within a Bayesian framework, by expressing global warming and sea-level rise as cumulative distribution functions that are much more likely to be exceeded at lower levels than higher levels (Jones, 2004; Mastrandrea and Schneider, 2004; Yohe, 2004). However, although this may be achieved for key global vulnerabilities, there is often no straightforward way to integrate local critical thresholds into a 'mass' damage function of many different metrics across a wide range of potential impacts (Jacoby, 2004).
Stakeholder involvement is crucial to risk, adaptation, and vulnerability assessments because it is the stakeholders who will be most affected and thus may need to adapt (Burton et al., 2002; Renn, 2004; UNDP, 2005). Stakeholders are characterised as individuals or groups who have anything of value (both monetary and non-monetary) that may be affected by climate change or by the actions taken to manage anticipated climate risks. They might be policy-makers, scientists, communities, and/or managers in the sectors and regions most at risk both now and in the future (Rowe and Frewer, 2000; Conde and Lonsdale, 2005).
Individual and institutional knowledge and expertise comprise the principal resources for adapting to the impacts of climate change. Adaptive capacity is developed if people have time to strengthen networks, knowledge, and resources, and the willingness to find solutions (Cohen, 1997; Cebon et al., 1999; Ivey et al., 2004). Kasperson (2006) argues that the success of stakeholder involvement lies not only in informing interested and affected people, but also in empowering them to act on the enlarged knowledge. Through an ongoing process of negotiation and modification, stakeholders can assess the viability of adaptive measures by integrating scientific information into their own social, economic, cultural, and environmental context (van Asselt and Rotmans, 2002; see also Chapter 18, Section 18.5). However, stakeholder involvement may occur in a context where political differences, inequalities, or conflicts may be raised; researchers must accept that it is not their role to solve those conflicts, unless they want to be part of them (Conde and Lonsdale, 2005). Approaches to stakeholder engagement vary from passive interactions, where the stakeholders only provide information, to a level where the stakeholders themselves initiate and design the process (Figure 2.2).
Current adaptation practices for climate risks are being developed by communities, governments, Non-Governmental Organisations (NGOs), and other organised stakeholders to increase their adaptive capacity (Ford and Smit, 2004; Thomalla et al., 2005; Conde et al., 2006). Indigenous knowledge studies are a valuable source of information for CCIAV assessments, especially where formally collected and recorded data are sparse (Huntington and Fox, 2005). Stakeholders have a part to play in scenario development (Lorenzoni et al., 2000; Barlund and Carter, 2002) and participatory modelling (e.g., Welp, 2001; van Asselt and Rijkens-Klomp, 2002).
Stakeholders are also central in assessing future needs for developing policies and measures to adapt (Nadarajah and Rankin, 2005). These needs have been recognised in regional and national approaches to assessing climate impacts and adaptation, including the UK Climate Impacts Programme (UKCIP) (West and Gawith, 2005), the US National Assessment (National Assessment Synthesis Team 2000; Parson et al., 2003), the Arctic Climate Impact Assessment (ACIA, 2005), the Finnish National Climate Change Adaptation Strategy (Marttila et al., 2005) and the related FINADAPT research consortium (Kankaanpaa et al., 2005), and the Mackenzie Basin Impact Study (Cohen, 1997).
The coping range of climate (Hewitt and Burton, 1971) is described in the TAR as the capacity of systems to accommodate variations in climatic conditions (Smith et al., 2001), and thus serves as a suitable template for understanding the relationship between changing climate hazards and society. The concept of the coping range has since been expanded to incorporate concepts of current and future adaptation, planning and policy horizons, and likelihood (Yohe and Tol, 2002; Willows and Connell, 2003; UNDP, 2005). It can therefore serve as a conceptual model (Morgan et al., 2001) which can be used to integrate analytical techniques with a broader understanding of climate-society relationships (Jones and Mearns, 2005).
The coping range is used to link the understanding of current adaptation to climate with adaptation needs under climate change. It is a useful mental model to use with stakeholders -
Self Mobilisation: stakeholders initiate the assessment and control its process, contracting skilled assistance to participate where needed
Partnership: stakeholders act as equal partners in process, contributing resources and taking ownership of the outcomes
Participation : stakeholders collaborate in process driven by a third party and are dependent on outside resources but can act to ensure process and results are relevant
Consultation : stakeholders are consulted by researchers to provide information which is then used to tailor the assessment process.
Information: stakeholders are involved in interviews or questionnaires but have no influence on the process
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