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

Introductionlimited importance for short-term climate changeprojections (Cox and Stephenson, 2007; Hawkinsand Sutton, 2009; Yip et al., 2011).Another source of uncertainty not explicitlymentioned in the list above is the downscalingof climate or climate impact projections. Mostprojections in this report cover all of Europe(i.e. EEA member and cooperating countries). Sucha broad coverage necessarily limits the level ofdetail at which regional climatic, environmental andother features can be considered, and the spatialresolution at which projections can be presented.Decisions on the management of climate-sensitiveresources at the national, regional and local levelsrequire more detailed projections at a higher spatialresolution than can be presented in this report. A keyelement of providing such detailed projections is thedownscaling of climate projections (see Chapter 2),which constitutes another important element ofuncertainty in climate and climate impact projects atthe national and subnational levels.Further information on sources of uncertaintycan be found in the uncertainty guidance ofClimate‐ADAPT ( 30 ).1.6.2 Addressing and communicating uncertaintyThe lack of perfect information is a common featurein all areas of policymaking. Uncertainties mustnot prevent taking decisions but it is in the interestof decision-makers to be aware of the degree ofuncertainty associated with specific data sourcesso that they can consider the range of plausibledevelopments in their decisions. The importance ofuncertainties about climate change and its impactsfor a particular decision depends on factors such asthe time horizon and reversibility of the decision, theimportance of climate factors for the decision, andthe costs of buffering the decision against uncertaindevelopments. For example, when uncertaintiesare very large, it is often (but not always) prudentto focus on 'no regrets' and 'win-win' adaptationstrategies that address adaptation to (uncertain)climate change jointly with other societal goals,thereby limiting the additional cost of the adaptationcomponent. This topic is addressed in more detailin the parallel report on Adaptation in Europe (seeSection 1.2.4).Compared to the 2008 report, increased efforts weremade in this report to describe the accuracy androbustness of data underlying indicators as clearlyas possible. The approach followed in this reportwas inspired by the considerable experience of theIPCC in communicating uncertainties (Mastrandreaet al., 2010) and by the NUSAP approach (Funtowiczand Ravetz, 1990). Over a period of 10 years, theIPCC has developed and refined a 'calibratedlanguage' to express the confidence in and/orlikelihood of specific findings, which is appliedin most key messages of IPCC reports. However,following the IPCC uncertainty guidance in thisreport is not feasible because the small number ofexperts involved in producing this report prohibitsquantitative expert assessments of confidence anduncertainty.In this report uncertainty is addressed by:1. choosing carefully the type of statement, makingclear the specific context and possibilities forgeneralisation;2. choosing the appropriate level of precision, fromthe existence of an effect to a precise value;3. reporting the pedigree of a statement, includingmain factors known to affect the confidence thatcan be put in a specific data set or conclusion.These three main elements of addressinguncertainties in this report are outlined below.Appropriate choice of type of statementSeveral different types of statements can bedistinguished in this report:1. observation of a climate variable;2. observation of a statistically significant (changein) trend of a climate variable;3. projection of a climate variable into the future;4. observation of a climate-sensitive 'impact'variable (i.e. a change in an environmental orsocial phenomenon that is sensitive to changesin climate);5. observation of a significant (change in) trend of aclimate-sensitive 'impact' variable;6. attribution of a change in a climate-sensitive'impact' variable to (anthropogenic) climatechange;( 30 ) See http://climate-adapt.eea.europa.eu/uncertainty-guidance.Climate change, impacts and vulnerability in Europe 201243