3012 20170106113920.0 10.1007/s11207-016-0970-6 DOI SCART-2017-0008 Dudok de Wit, Thierry Uncertainties in the Sunspot Numbers: Estimation and Implications 2016 Sunspot number series are subject to various uncertainties that are still poorly known. The need to understand these better was recently highlighted by the major revision of the international Sunspot Number (Clette et al., in Space Sci. Rev. 186, 35, 2014). We present the first thorough estimation of these uncertainties, which behave as Poisson-like random variables with a multiplicative coefficient that is time- and observatory-dependent. We provide a simple expression for these uncertainties, and reveal how their evolution in time coincides with changes in the observations and processing of the data. Knowing their value is essential for properly building composites out of multiple observations, and for preserving the stability of the composites in time. STCE Sunspots Statistics Lefèvre, Laure Clette, Frédéric Solar Physics 291 2016 9-10 2709-2731 laure.lefevre@observatoire.be published in REFERD