IGU Thematic Conferences are held from time to time and are designed to encourage several IGU Commissions to collaborate around a joint theme. Thematic conferences are genuinely international (and therefore respect the two official IGU languages), have a clear theme or topic that is of broad interest and that it specifically involve at least four IGU commissions. Each thematic conference is approved by the IGU Executive Committee and applications should be made 12-18 months in advance of the event. An IGU thematic conference can be proposed to the EC by one or more commissions and/or by a national committee; indeed, the involvement of the relevant national committee(s) in these thematic conferences is considered essential. Every effort should be made to encourage broad international participation. There is not normally more than one thematic conference during an IGU Congress or Regional Conference year, and not more than two in a year in which there is no other major IGU event.