Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Changes in the climate systemBox 2.1General circulation models (GCMs) and regional climate models (RCMs)General circulation models (GCMs) are numerical models that represent key physical and chemical processes inall components of the global climate system (see Figure 2.1). GCMs are the most advanced tools for simulatingthe response of the global climate system to different emissions scenarios for GHGs and aerosols. GCMs depictthe climate using a three-dimensional (3D) grid over the globe. The GCMs used in the IPCC AR4 typically simulateatmospheric processes at a horizontal resolution of between 100 and 300 km, with 20 to 60 vertical layers. Oceanprocesses were simulated at a horizontal resolution of between 20 and 200 km, with up to 30 vertical layers.Some more recent GCMs have a somewhat finer horizontal resolution but their resolution is still quite coarserelative to the scale of exposure units in most climate impact assessments.Regional climate models (RCMs) can be used to bridge the coarse-resolution outputs from GCMs with thehigh‐resolution climate data needs of regional impact assessments. RCMs cover a limited area of interest, such asEurope or an individual country (see Figure 2.3). They are embedded into GCMs, which prescribe the large-scaleclimate features. RCMs typically have a horizontal resolution of between 5 and 50 km. Their higher resolutionallows for a better representation of topographic features (e.g. mountain ranges) and of regional-scale climatephenomena. As a result they can provide better projections of changes in regional precipitation patterns and incertain weather extremes. RCMs have been used to relate future climate change in specific locations to the currentvariability of climate within Europe. For example, simulations with two RCMs have suggested that the climate ofthe city of London at the end of the 21st century under a high emissions scenario (SRES A2) would be similar tothe current climate in south-west France or northern Portugal, respectively (Kopf et al., 2008).Global and regional climate models have recognised weaknesses. Their simulations of past and current climateshow some deviation from the observed climate. Furthermore, different models provide somewhat differentclimate projections when forced with the same emissions scenario (see Section 2.1.4). Nevertheless, the scientificcommunity is confident that climate models provide credible quantitative estimates of future climate change sincethese models are based on fundamental physical laws and are able to reproduce the key features of observedclimate change.Figure 2.3Components needed for modelling climate change and its impactsGCMRCMGHG emission andconcentration scenarios. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .ClimatemodelsImpactmodelsWaterAOGCM projectionsRegionalisationImpactsEnergyFoodEcosystemsHealthSource: Blaz Kurnik (EEA).Downscaling of climate projections may be obtained by RCMs and the empirical-statistical downscaling modelling(ESDM). ESDM can effectively correct or refine climate variable projections provided by GCMs or RCMs and reducethe spread of projections given by a GCM/RCM ensemble. Application of ESDM is particularly beneficial to supportlocal-scale climate projections and adaptation in mountain regions where many different precipitation regimes mayexist within a GCM/RCM grid cell.52 Climate change, impacts and vulnerability in Europe 2012