On July 31, 2003, an Earth Observations Summit was held in Washington D.C. that, if its proponents are correct, will herald a concerted effort to provide the monitoring of our global environment that appears to many to be essential in addressing how and why our earth is changing. The oceans, covering 71% of the earth’s surface and containing 96% of its water, are a vital element that needs to be adequately observed so that it can be satisfactorily represented in climate simulations. We are indeed fortunate that most of the systems and infrastructure elements that are needed to observe the oceans are already in place. It was not always so and our present relatively strong position is due to efforts by the science community over the past 20 years. Twenty years is a rather short period, certainly in terms of the 125 year lifetime of scientific ocean exploration if we mark its start with the 1873–1876 voyage of HMS Challenger. Yet these two decades have seen a revolution in our ability to observe the oceans and understand how they “work”. This revolution (from a physical standpoint at least) was driven by the Tropical Ocean Global Atmosphere study (TOGA) and the World Ocean Circulation Experiment (WOCE). Both were part of the wider World Climate Research Program (WCRP).