The latest numbers released from Journal Citation Reports (JCR), published annually by Thomson Reuters, show large increases in the impact factor (IF) for several AGU journals. IFs are one way for publishers to know that readers have found their journals useful and of value in research.
A journal's IF is calculated by taking the total number of citations to articles published by a given journal in the past 2 years and dividing it by the total number of papers published by the journal in the same time period. More generally, it can be seen as the frequency with which articles in a journal have been cited over the past year. The numbers speak for themselves (see Table 1).