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Prior to the inclusion of E-OBS in the Copernicus Data Store, users were encouraged to register as an E-OBS user (although not mandatory to be able to download the dataset). By registering as an E-OBS user, they are notified when a new version is available and in case a problem has been found with the dataset. This registration system is used to track the number of registered and confirmed users. Figure 2 shows the cumulative number of users since the start of this system (early 2009) and the number of new users per month. Since this registration is not mandatory, it is expected that there are more users of the E-OBS dataset than visualized here. Figure 3 shows a pie chart of the user groups of ECA&D and E-OBS based on a survey from 2013, which shows that the use of E-OBS has spread beyond the climate community.
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The calculation of the European averaged temperature is documented by Van der Schrier et al. (2013). In this study, a quantitative analysis of the uncertainty sources to the European average temperature indicates that the uncertainties due to urbanization, statistical interpolation, and the potential inhomogeneities in the input records to E‐OBS dominate the total uncertainty estimate for the European-averaged temperature.
The uncertainty estimate in this metric is used to make a comparison between E-OBSv6.0 and global observational datasets and global reanalyses. Although E-OBSv6.0 differs considerably with the latest versions of E-OBS (station density has increased, the method to calculate the gridded temperature estimate and the uncertainty has changed, and the spatial resolution has increased), the temperature averaged over the European continent and averaged over the year will not be dramatically affected as the averaging in time and space makes this metric independent of the improvements in the fine-scale structure. The increase in station density makes that the uncertainty estimate of the statistical interpolation has decreased, making the uncertainty estimates for the early versions of E-OBS somewhat pessimistic for the latest versions.
Figure 9: European averaged temperature with respect to the 1961-1990 climatology as calculated for E-OBSv6.0 compared to global observational datasets (left) and global reanalysis (right). The lower plot gives the E-OBS uncertainty margins in grey boxes and the difference between E-OBS and the global datasets (Van der Schrier et al. 2013)
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