It is well established that the global mean temperature rose rapidly during the late 20th century. Yet despite the addition of over 100 billion tons of carbon dioxide over the first decade of the 21st century, the rate of global mean temperature rise has been much smaller during this period. If the current trend continues at the same rate as in the past decade, the temperature rise will soon deviate beyond the 95% confidence limit of the ensemble mean from the collection of the most sophisticated climate models used in IPCC assessment, as shown in the figure. The mismatch between the accelerating rate of rise of greenhouse emission and the apparent lack of an instantaneous global mean temperature response poses a puzzling scientific question with urgent policy implications. Of all the potential causes of the current hiatus in the warming, the ocean is the most likely culprit. Yet, the ocean, with its great depth and enormous heat capacity, is among the least understood components of the climate system. Observational data seem to suggest that the oceans indeed exhibit robust decadal to multi-decadal scale oscillatory variations but the physical processes that come into play in creating them are elusive. In order to make reliable prediction of the future climate variations, we need to understand these crucial processes. We hope that by convening this Forum, we will be able discuss the issues, formulate possible scientific programs and suggest future actions needed to address this pressing problem.