This assessment is a critical analysis of the existing body of knowledge concerning the risks and opportunities that climate change presents for Canada. This process required consideration of historical climate trends, projected climate change, climatic sensitivity of key systems, and current and future adaptive capacity. New studies and research were not commissioned for the purposes of the assessment.
Authors were directed to draw from three main sources:
- Peer-reviewed published literature: Peer-reviewed published literature was the primary source of material for the assessment. There is a large and growing body of climate change literature focused specifically on Canada, and international papers of relevance to understanding Canada's vulnerability. In addition, there is a wealth of peer-reviewed information relevant to climate change impacts and adaptation outside climate change journals. The authors were therefore encouraged to draw from other fields of research, such as natural disasters, land-use management, political economics and planning.
- Grey literature: Grey literature, including government reports, non-peer-reviewed papers in a variety of publications, workshop reports and consultant reports was also used as reference material. Such sources contribute significantly to understanding vulnerability to climate change, and often are the only place to access the most recent and locally relevant information. Authors' discretion was used to evaluate the quality and suitability of the grey literature.
- Local/practitioner knowledge: This assessment recognizes that local knowledge, frequently obtained through communication with practitioners, complements that obtained from scientific sources. Given the applied nature and local scale of many adaptation measures, direct experience is rarely captured in the scientific literature. For this reason, the report occasionally cites personal communications to capture and attribute this knowledge.
As noted in Chapter 1, the scientific information presented in this assessment includes traditional (Aboriginal) knowledge. This knowledge is captured in all three sources described above. Material included in each chapter broadly reflects the scope of information available through the sources noted above. The volume of material available on a specific topic, however, does not necessarily reflect the relative significance of that issue at a regional or national level. Indeed, there is only very limited information available on some important aspects of impacts and adaptation, such as economic analyses. Hence, assessment of the significance of available knowledge reflects the expert judgement of the lead and contributing authors of each chapter, in their areas of specialization. The authors were also asked to identify key knowledge gaps. General guidance documents addressing scope, goals and key concepts were provided to the writing teams, but decisions on how information on any given region could be most effectively presented was left to the authors. Peer review by both science and policy experts in academia and government helped to guide the final version of this report.
5.2 LIKELIHOOD AND CONFIDENCE
Uncertainty is an inherent component of any climate change analysis. While it may be possible to identify the major sources of uncertainty (e.g. in climate change projections), full quantification is rarely possible. This is particularly true for impacts and adaptation studies, which typically involve multiple steps, each introducing uncertainties that are propagated through the study (i.e. cascading uncertainties). Uncertainties related to socioeconomic factors, which influence both future emission pathways and adaptive capacity, are especially difficult to assess (Manning et al., 2004). These uncertainties make it challenging to reach strong conclusions on the likelihood of an outcome being realized, or to determine the confidence that should be associated with a particular statement.
Many science assessments, including the Arctic Climate Impact Assessment (ACIA) and those of the Intergovernmental Panel on Climate Change (IPCC), adopt a probability-based nomenclature for expressing likelihood and/or confidence. Assignment of a particular term (e.g. likely, very likely) is based upon expert evaluation of the volume and agreement of the scientific literature, drawing from multiple lines of evidence that include observed trends, experiments, model simulations and theory (Huntington et al., 2005b).
For this assessment, it was deemed neither practical nor meaningful to adopt a probability-based terminology. When undertaking analysis at the regional or sub-regional level, the generally small volume of information available on any specific topic dictates that statements of likelihood and confidence will dominantly reflect expert judgement, and are necessarily qualitative. Authors were encouraged to focus on communicating both the likelihood and confidence of their conclusions using common-sense language rather than prescribed expressions. Authors were generally able to express greater confidence when the quantity and quality of research available on the issue was high. Expressions of likelihood are strongest where projections are consistent with historical trends and/or well-established climate-system relationships, and supported by independent modelling analysis.
5.3 USE OF SCENARIOS
This assessment does not focus on any particular climate scenario or set of scenarios in the discussion of future climate change. As an integration and analysis of previous studies that took different approaches to the issue of climate scenarios and related assumptions, it tries to place the results of those studies in the context of a complete range of plausible climate futures.
Each regional chapter includes a section describing projected climate change for the region, which have been derived from climate change experiments undertaken with seven global climate models (GCMs), using an illustrative scenario from each of the six emissions scenario groups in the Special Report on Emissions Scenarios (SRES). These were the most recent scenarios available at the start of this assessment process (2005), and have been constructed in accordance with the recommendations of the IPCC Task Group on Data and Scenario Support for Impact and Climate Assessment (IPCC-TGICA). The GCMs selected for use conform to this group's recommendations, and the scenarios indicate the climate changes (with respect to 1961 -1990) for the 2020s, 2050s and 2080s, the three future time periods recommended for study. Scenario results were provided to the authors of each chapter as scatterplots, maps and box-and-whisker plots (Appendix 1). The decision regarding which of these graphic formats appear in the published chapters was left to the lead authors. Some chapters present additional climate scenario information, in which case the models and emission scenarios used are specified.
Long-term socioeconomic scenarios suitable for climate change impacts and adaptation studies do not exist for all regions of Canada. As a result, authors of each chapter were encouraged to use whatever relevant data was available. Extensive data on demographic and socioeconomic historical trends are available from Statistics Canada at various scales (e.g. national, provincial, census metropolitan area). Examples of trends of relevance to vulnerability assessment include rural to urban migration, changing age distributions, and trends in income level and gross domestic product (see http://www41.statcan.ca/ceb_r000_e.htm). Statistics Canada also provides projections of future population totals and age distributions by sex for the years 2011, 2016, 2021, 2026 and 2031. Other sources of socioeconomic data are referenced in individual chapters of this assessment.