There is broad consensus that human emissions of greenhouse gases— principally carbon dioxide, but also methane and nitrous oxide—contribute to global warming. Because of water’s high capacity for heat retention, the warming effect is not nearly as clear in the atmosphere as it is in the oceans, which have warmed by approximately 0.5ºC (0.9ºF) over the past 65 years. Warming seas translate into numerous negative impacts, including coral reef bleaching, fish stock depletion, Gulf Stream disruption, stronger hurricanes, and, of course, a rising sea level. In order to better understand the challenges presented by sea level rise, in this study we review recent scientific publications and seek both to explain the phenomenon and to predict future effects. In order to gauge the potential benefits of a climate stewardship policy, we illustrate a range of possible impacts below one meter of sea level rise for selected sites both in the United States and worldwide, with three different scenarios for the 21st century in the background. The three scenarios are based on potential greenhouse gas concentrations that would result of three different types of climate policies.