Recently, the Citescore for 2016 has been released. In the Earth and Planetary Sciences category, the journal Nature Geoscience topped the Citescore list, followed by Earth-Science Reviews.
Here is the definition of CiteScore from Elsevier and how it is computed:
“CiteScore is a simple way of measuring the citation impact of serial titles such as journals. Serial titles are defined as titles which publish on a regular basis (i.e. one or more volumes per year). CiteScore calculates the average number of citations received in a calendar year by all items published in that journal in the preceding three years. The calendar year to which a serial title’s issues are assigned is determined by their cover dates, and not the dates that the serial issues were made available online.”