Global Warming is one of the most significant environmental issues of the early 21st Century. Sea-level rise from the melting of polar ice sheets would be one of the most significant effects of global warming.
Projecting the extent of such a rise 200 years in the future is difficult, given the variables involved. However, each new scientific discovery points to an increased rate of glacier melt and consequent sea level rise. The Arctic impact assessment is a start on such an analysis.
Polar warming by the year 2100 may reach levels similar to those of around 130,000 years ago associated with sea levels several meters above modern levels; both the Greenland Ice Sheet and portions of the Antarctic Ice Sheet may be vulnerable.
The record of past ice-sheet melting indicates that the rate of future melting and related sea-level rise could be faster than widely thought. A scenario contemplating a combination of melting from the Greenland ice sheet as well as that of West Antarctica could bring about a sea level rise of 6 meters or more.
Changing coastlines worldwide due to alternative future sea level changes can be demonstrated through the internet. One site, flood.firetree.net enables the viewer to experiment and view the effect of alternative sea level rises using elevation data provided by NASA. The University of Arizona's Department of Geosciences has a site showing the impact of sea level rise on vulnerable areas around the earth. Climate Central created an interactive map in 2013 which illustrated for the mainland USA the potential impacts of a 1 to 10 foot rise in sea level. The impact of rising seas in the San Francisco Bay Area was presented in a 2007 public radio report.
The satellite images below demonstrate the potential impact on five (5) different coastal areas of a 6 meter (20 feet) rise in sea level. The scenario assumes a failure of leading industrial nations, such as the United States, and emerging industrial giants, such as India and China, to seriously reduce emissions of the "greenhouse gases" linked to global warming. Sources for changed shoreline were actual contour lines in the case of the Bay Area and the University of Arizona website.