Global commons is a concept to understand commons which are not limited to local or national boundaries.  Commons, in general, provide public goods which are non-exclusive and non-discriminately but are easily exploited by free riders who only enjoy the fruits of commons but avoid responsibility as a member of community.  In fact, studies of commons have often been associated with studies of tragedy of commons.  Scholars have studied global agenda such as climate change or water resource management by elaborating the concepts of global commons as well as its tragedy.