The Global Observing System, a component of the WMO Integrated Global Observing System (WIGOS), is an extremely complex undertaking, and perhaps one of the most ambitious and successful instances of international collaboration of the last 60 years, initiated in support of the world Weather Watch, and then increasingly in support also of climate monitoring. It consists of a multitude of individual surface- and space-based observing systems owned and operated by a plethora of national and international agencies with different funding lines, allegiances, overall priorities and management processes.