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

Introductionimmigration will be low, 55–70 % of the NUTS2regions in Europe will experience a decline of thelabour force by 10 % or more. In most regions ineastern and southern parts of Europe, the labourforce may even decrease by more than 30 %. Use ofsuch detailed demographic and macro-economicprojections within future EU-wide climate changevulnerability assessments could potentially improvethe quality and consistency of such assessments.1.6 Uncertainty in observations andprojectionsData on observed and projected climate changeand its impacts is always associated with someuncertainty. This section discusses the main sourcesof uncertainty relevant for this report, and howuncertainties are addressed and communicated inthis report, in particular in the key messages. Notethat the term 'uncertainty' is used by scientists torefer to partial, or imperfect, information. Thus, thedirection or even the approximate magnitude ofa phenomenon may be known although the exactmagnitude is not known. For example, a scientificprojection of global mean temperature for a givenemissions scenario may report a best estimate of3 °C, with an uncertainty range of 2–4.5 °C. Theuncertainty interval reflects the impossibilityto forecast exactly what will happen. However,knowing that it is virtually certain that the Earthwill continue to warm and that the future warmingis likely within a certain range still provideshighly relevant information to decision-makersconcerned with climate change mitigation as well asadaptation.1.6.1 Sources of uncertaintyUncertainties in indicators presented in this reportarise primarily from the following sources. Notethat some sources of uncertainty can be quantifiedwhereas others cannot. Furthermore, some of themcan in principle be reduced by further researchwhereas others cannot.1. Measurement errors resulting from imperfectobservational instruments (e.g. rain gauges) and/or data processing (e.g. algorithms for estimatingsurface temperature based on satellite data).2. Aggregation errors resulting from incompletetemporal and/or spatial data coverage. Mostindicators presented in this report combinemeasurement from a limited number of locations(e.g. meteorological observation stations) andfrom discrete points in time to make aggregatestatements on large regions and for wholetime periods. Such an aggregation introducesuncertainties, in particular when the measurenetwork is scarce and when the phenomenonexhibits large variations across space and/ortime.3. Natural climate variability resulting fromunpredictable natural processes either withinthe climate system (e.g. atmospheric and oceanicvariability) or outside the climate system(e.g. future volcanic eruptions).4. Future emissions of greenhouse gases determinethe magnitude of the human influence on theclimate system and therefore the magnitude andrate of future climate change. Controlling (net)GHG emissions is the only way, besides highlycontroversial geo-engineering, to limit globalclimate change.5. Uncertainties in climate models resulting from anincomplete understanding of the Earth system(e.g. dynamic ice sheet processes or methanerelease from permafrost areas and methanehydrates) and/or from the limited resolutionof climate models (e.g. hampering the explicitresolution of cloud physics). These uncertaintiesare particularly relevant in the context ofpositive and negative feedback processes.6. Complex interaction of climatic and non‐climaticfactors. This complex cause-effect web hampersthe attribution of observed environmental orsocial changes to past changes in climate as wellas the projection of future climate impacts.7. Future changes in socio‐economic, demographic andtechnological factors as well as in societal preferencesand political priorities. Changes in non‐climaticvariables interact with climate change todetermine the impacts on environment andsociety. Changes in preferences affect whethera certain 'climate impact' (e.g. a decrease inbiodiversity) is seen as a small or big problem;such changes are particularly relevant in theformulation of long-term adaptation policies.The relative importance of the various sourcesof uncertainty depends on the target system, theclimate and non‐climate factors it is sensitiveto, and the time horizon of the assessment. Forexample, uncertainty about future emissions oflong-lived GHGs becomes the dominant source ofuncertainty for changes in global mean temperatureon time scales of 50 years or more but it is of42 Climate change, impacts and vulnerability in Europe 2012