2020-1 prerelease containing data from the atmospheric network of ICOS Research Infrastructure for 23 stations and 62 vertical levels at Gartow, Hohenpeißenberg, Hyltemossa, Ispra, Jungfraujoch, Karlsruhe, Křešín u Pacova, Lindenberg, Lutjewad, Monte Cimone, Norunda, OPE, Ochsenkopf, Pallas, Puy de Dome, La Réunion, SMEAR-II, Steinkimmen, Svartberget, Torfhaus, Trainou, Utö and Zeppelin Observatory. This collection contains the final quality controlled hourly averaged data for the mole fractions of CO2 measured at the relevant vertical levels of the measurements stations, for the period September 2015-May 2020. All stations follow the ICOS Atmospheric Station specification V1.3 (https://doi.org/10.18160/SDW6-BX90) and are certified as ICOS atmospheric stations Class I or II. Data processing has been performed as described in Hazan et al., 2016 (doi:10.5194/amt-9-4719-2016).