world monthly means database


Monthly means were calculated as far back in time as possible from hourly means retrieved from the WDC in Edinburgh (previously in Copenhagen). They were systematically checked for internal consistency and by comparing them with annual means from the WDC Edinburgh and with the CM4 geomagnetic model. Since 2005, INTERMAGNET data are used.
Anomalous data are not present in the database, awaiting resolution of the inconsistencies by the relevant observatories.

Monthly means are archived using a new, specific file format.

This database involves only INTERMAGNET magnetic observatories and is updated every year as soon as definitive data are available.

Any publication or website making use of data from this database should acknowledge the institution(s) in charge of the corresponding observatory(s). It should also acknowledge INTERMAGNET for facilitating the collection and dissemination of observatory data worldwide.


Chulliat, A. and K. Telali, World Monthly Means DataBase Project,, Publ. Inst. Geophys. Pol.
Acad. Sc., C-99 (398), 2007.

Web access to the database

Data download also possible via FTP
server: ftp.bcmt.fr, user name: bcmt_public, password: bcmt

Contacts: telali@ipgp.fr