ClimateChange Assessment Guide.pdf - University of Waterloo

Guide for Assessment of Hydrologic Effects of Climate Change in Ontario60This ensures that the hydrologic assessment exploresa wide range of possible impacts and adaptationoptions to inform decision and policy making.• Criterion 5: Accessible. The climate change scenariosshould be straightforward to obtain, interpret andapply for the hydrologic impact assessment.The process of developing GCM-based climatechange scenarios for hydrologic impact and adaptationassessments is a challenging endeavour; there arenumerous factors to consider and there is an ongoingevolution of climate modelling results and impactsand adaptation methodologies. The key issue is howto develop climate change scenarios that reflectthe future uncertainty in the climate system yet arerobust enough to provide guidance for decisionmaking?The hydrologic assessment community shouldexplore the range of uncertainty and use as manyclimate change scenarios as possible in order to fullyinvestigate the:• Scope of future conditions;• Impacts that will result; and• Potential adaptation strategies.This section was developed to guide the user throughkey considerations for:• Selecting the climatological baseline; and• Selecting candidate GCM output for scenariodevelopment.Environment Canada has developed the CanadianClimate Change Scenarios Network (CCCSN), a websitefor disseminating climate change scenarios (and otherclimate change impact and adaptation information). Thissection of the Guide relies on the access to the toolsand data on the CCCSN (www.cccsn.ca) to develop theGCM-based climate change scenarios. Users of thisGuide should be aware that all of the website addresses,provided in this Guide, are subject to possible changein the future as information distribution systems areupgraded.6.4.1 Define Baseline Climate or Current ConditionsdefBaseline/Reference • The baseline (or reference)is any datum against which change is measured.It might be a “current baseline”, in which case itrepresents observable, present-day conditions.It might also be a “future baseline”, which isa projected future set of conditions excludingthe driving factor of interest. Alternativeinterpretations of the reference conditions cangive rise to multiple baselines (IPCC-TGICA et al.,2007).An initial step in any hydrologic assessment ischaracterizing the present-day or recent climatein a region – the climatological baseline. Since thebaseline establishes the reference from which changes,impacts and adaptations are assessed, its selection (inconjunction with climate change scenarios used) canstrongly influence the outcome of a climate impactassessment. Carter et al. (1994) recommended thatthe baseline for the current climate meet the followingcriteria:• It represents present-day or recent “average, normal”climate in the study region;• The time series is of sufficient duration to encompassa range of climatic variations, including a number ofsignificant weather anomalies/extremes (e.g., severedroughts, high precipitation events and warm spells);• The data for the critical parameters/elements for theassessment are abundant, adequately distributedover the study area and readily available;• The data meet standards for high quality observedclimatological data with few missing data; and• The period overlaps sufficiently with baseline periodselected for the GCM-based baseline climate (usually1961 to 1990) in calculation of change fields forexample.