Media from C3S website may be used for projects or publications under the condition that the source is acknowledged, in line with the picture, as follows:
Credit: ECMWF, Copernicus Climate Change Service (C3S)
The above applies to media published on the C3S website, like text, graphs, maps and photographs. It does not apply to data products, those are governed by their respective licenses and the text of the licenses sets out how products and derived data and media should be attributed to the Copernicus programme.
To reference or acknowledge data from C3S in a publication, please refer to "Citations" on the dataset entry of the Climate Data Store (CDS).