Abstract: The 2004 tsunami has generated a call for a global early warning system. Political issues may prevent this from occurring soon or at all. This paper explores previous experience with informal early warning systems from the Year 2000, Y2K, rollover. Informal early warning systems, IEWS, are cooperative systems formed outside of direct government control, usually from nonprofit or industry organizations. The two discussed utility Y2K IEWS were formed through an industry group and within a single multinational corporation. The paper concludes with lessons learned from the design and implementation of these systems.