ClimateChange Assessment Guide.pdf - University of Waterloo

Introduction3change research and incorporate new understandingof the future distribution and intensity into impactassessments as it becomes available.is meant to be generic, it is suited to water resourceinvestigations with some minor modifications.Undoubtedly, there will be considerable adjustmentrequired in treatment of input data and in choice ofhydrologic modelling procedures in order to incorporateconsiderations of climate change into hydrologicstudies in which potential future changes to the intensityand frequency of storms and extreme precipitationevents are of concern. Estimates of future intensity andfrequency characteristics are likely to be determinedusing a combination of risk assessment techniques andtrend analysis; whereas, the future climates determinedusing the guidance provided in this document arebased upon deterministic modelling using sophisticatedGCMs.Some aspects of stormwater management,subwatershed studies, and dam safety and operationsstudies require investigation of peak storm flows andfrequencies/risks; however, this aspect is not addressedby the guidance provided in this document. This Guidefocuses on methods and procedures for developingfuture climates that can be used as input to continuousstreamflow generating and groundwater flow modelsthat address water balance and streamflow issues.The Guide recommends the application of climatedownscaling techniques that investigate climatevariability. However, at this time, the availability ofnecessary online climate data and the general widedisparity among simulation results using these climatedownscaling techniques, especially with respect to futureprecipitation patterns, precludes widespread adoptionof downscaling for the purpose of refining futurerainfall characteristics. As such, in this Guide, the use ofdownscaling techniques is recommended only as a firstestimate of potential future climate variability. In thisregard, the downscaled climates are not recommendedfor use in studies where the subject of investigationis the future intensity and frequency of extremeprecipitation events and the resulting streamflow.1.3 General ApproachThe Intergovernmental Panel on Climate Change (IPCC)provides guidelines for conducting assessments ofclimate change impact and adaptation strategies (Carteret al., 1994; IPCC-TGICA et al., 2007). Since the approachFigure 1.1 Climate change impact assessment stepsThe approach proposed in this Guide is shown in Figure1.1. Each step is developed and explained in Chapter 6,with references to the relevant subsections in this figure.The assessment process should be formalized, as shown,to ensure that decisions allow for balancing objectiveswith capabilities and for rationalizing uncertainty giventhe resolution and level of effort. In many studies,several of the steps in this approach would already becompleted and the steps relating specifically to climatechange impact assessment (i.e., steps 4 through 7)need only be applied. However, it is good practice in allassessments to review each step.The process includes feedback loops as indicatedin Figure 1.1. The first return loop at the third stepwould be followed when an approach is found to beunsuccessful or otherwise unsuitable at the hydrologicmodel testing step. The second return loop at the sixthstep would be followed when additional or differentscenarios are required or when the assessment hasnot achieved all of the objectives and a revised ordifferent approach is required. The last loop followingrecommendations and follow-up could representsituations where recommendations include anotherassessment with a new set of objectives or at least anew set of scenarios.