Determining how much sea level rises or falls along coastlines is complicated by the fact that the sea surface continually fluctuates. For instance, waves and tides produce cyclic changes in the surface that vary over a period of seconds to hours. Strong storms, rapid runoff from coastal streams, and earthquakes generate localized, one time increases in sea level like storm surges, coastal flooding, and tsunamis. Finally, over a much larger and longer span, changes in the volume of the oceans result in global changes in sea level.
It is the latter that is of interest to any discussion about climate change impacts. During the past few millennia changes in global sea level were largely a product of thermal expansion of seawater and changes in planetary ice cover. The idea of thermal expansion of sea water is simply that water increases in volume as it warms. Modeling of sea level change over the past two centuries indicates that this expansion has been a major contributor to the observed rise in sea level. Though a lesser factor, diminishing ice cover is still significant since shrinking land ice (glaciers and ice caps) contributes additional water to the oceans.
A significant risk of likely global sea level rise is that around 10% of the world’s population live in coastal areas are less than 10 m above sea level, with an additional 30% loving with 100 km of the coast. Furthermore, with nearly 10% of the world’s cities being located on or near coastlines the issue of rapidly rising sea level poses a number of major development issues. Each community faces a complex mix of specific issues related to their natural setting, size, and population character. These activities are designed to look at these factors.