## 1 Introduction
During 1984-2000, significant increasing trends in SSR, equal to 2.4 Wm\({}^{-2}\)decade\({}^{-1}\), were found in the International Satellite Cloud Climatology Project-D2 series (ISCCP-D2) satellite-based analysis by [10]. Furthermore, a global solar brightening of 1.6 Wm\({}^{-2}\)decade\({}^{-1}\) between 1983 and 2001 has been estimated by [35] using satellite retrievals (ISCCP-D1), associated with a decrease of clouds. The assessment made by [36] using Global Energy and Water Exchanges Project- Surface Radiation Budget version 2.8 (GEWEX-SRB V2.8) data, revealed a dimming equal to 2.51 Wm\({}^{-2}\)decade\({}^{-1}\) between 1983 and 1991, followed by a brightening of 3.17 Wm\({}^{-2}\)decade\({}^{-1}\) from 1991 to 1999, and then a subsequent dimming of 5.26 Wm\({}^{-2}\)decade\({}^{-1}\) during 1999-2004, yielding an overall global brightening of 0.25 Wm\({}^{-2}\)decade\({}^{-1}\) during 1983-2004. An overall dimming of \(-\)2.0 Wm\({}^{-2}\) from 1920 to 2000 has been computed by [32] that was consistent with the simulations from 10 models implemented in United Nations Intergovernmental Panel on Climate Change--Fourth Assessment Report (IPCC-AR4) that show a global dimming of \(-\)1 to \(-\)4 Wm\({}^{-2}\) during the 20 th century. They also found dimming from 1968 to 1977 followed by brightening during the 1980s and 1990s. Also, a study by [34] using a radiation transfer model with input ISCCP-D2 satellite data for the period 2000-2007 found a solar dimming in the Southern Hemisphere, due to increasing aerosols and clouds, but without a clear signal of dimming or brightening in the Northern Hemisphere, where a dimming was mostly observed over the oceans and a slight brightening over land. Slightly extending the study period, through to 2009, the same authors [12] found again a strongerdimming in the Southern Hemisphere along with a smaller dimming in the Northern Hemisphere. Moreover, a brightening equal to +0.03 Wm\({}^{-2}\)decade\({}^{-1}\) has been estimated by [37] using retrieved Clouds and the Earth's Radiant Energy System (CERES) satellite SSR data for the period 2001-2012. The same authors using ISCCP-FD SSR data estimated a stronger dimming of \(-\)5.05 Wm\({}^{-2}\)decade\({}^{-1}\) during 2000-2009 and a weaker dimming of \(-\)1.15 Wm\({}^{-2}\)decade\({}^{-1}\)during 1984-2009. All these results highlight the complex nature of GDB patterns in terms of spatial and temporal variability. Contrasting signs of SSR trends appear over adjacent areas, whereas the sign of GDB is sensitive to the selected study period, possibly changing by extending the study period by a few years, especially when relatively short periods are assessed. All these complexities point to the need for assessing GDB over as long as possible time periods and utilizing homogeneous SSR data sets. Reanalysis SSR products, that combine observations with models, have the advantage of providing full spatial coverage and long temporal coverage and therefore have been widely used in the atmospheric sciences and climate change studies [39]. Some of the reanalysis products are: the NCEP-NCAR, NCEP-DOE and Climate Forecast System Realysis (CFSR) from National Centers for Environmental Prediction and National Center for Atmospheric Research (NCEP) [40]; ERA-5, which replaced the ERA-Interim from European Centre for Medium-Range Weather Forecasts (ECMWF) [41]; the JRA-55 from Japan Meteorological Agency (JMA) [42]; the National Oceanic and Atmospheric Administration (NOAA)-CIRES-DOE 20 th Century Reanalysis V3 [43] and the Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) reanalysis of the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC)'s Global Modeling and Assimilation Office (GMAO). Products from these Reanalyses have been used to provide climatological assessments of SSR.