Statistical issues about solar–climate relations
1Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS-UVSQ 8212, IPSL, Gif-sur-Yvette, France
2Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement, UMR 6635, Aix-en-Provence, France
3Météo-France, Division de la Climatologie, Toulouse, France
4Laboratoire de Météorologie Dynamique, UMR 8539, IPSL, Ecole Normale Supérieure, Paris, France
5Centre Européen de Recherche et Formation Avancées en Calcul Scientifique, Toulouse, France
Abstract. The relationship between solar activity and temperature variation is a frequently discussed issue in climatology. This relationships is usually hypothesized on the basis of statistical analyses of temperature time series and time series related to solar activity. Recent studies (Le Mouël et al., 2008, 2009; Courtillot et al., 2010) focus on the variabilities of temperature and solar activity records to identify their relationships. We discuss the meaning of such analyses and propose a general framework to test the statistical significance for these variability-based analyses. This approach is illustrated using European temperature data sets and geomagnetic field variations. We show that tests for significant correlation between observed temperature variability and geomagnetic field variability is hindered by a low number of degrees of freedom introduced by excessively smoothing the variability-based statistics.