|Figure 1: U.S. Sea Level Trends
Source: Monthly and Annual Mean Sea Level Station Files from the Permanent Service for Mean Sea Level (PSMSL) at the Proudman Oceanographic Laboratory
Sea levels are rising worldwide and along much of the U.S. coast. Tide gauge measurements and satellite altimetry suggest that sea level has risen worldwide approximately 4.8-8.8 inches (12-22 cm) during the last century. A significant amount of sea level rise has likely resulted from the observed warming of the atmosphere and the oceans.
According to the Intergovernmental Panel on Climate Change (IPCC), the primary factors driving current sea level rise include:
Other factors may also be responsible for part of the historic rise in sea level, including the pumping of ground water for human use, impoundment in reservoirs, wetland drainage, deforestation, and the melting of polar ice sheets in response to the warming that has occurred since the last ice age.
Considering all of these factors, scientists still cannot account for the last century's sea level rise in its entirety. It is possible that some contributors to sea level rise have not been documented or well-quantified.
The rate of sea level rise increased during the 1993-2003 period compared with the longer-term average (1961-2003), although it is unclear whether the faster rate reflects a short-term variation or an increase in the long-term trend.
While the global average sea level rise of the 20th century was 4.4-8.8 inches, the sea level has not risen uniformly from region to region.
In the United States:
For an interactive map showing sea level trends throughout the U.S., visit NOAA's Sea Levels Online.
Globally (IPCC, 2007):
Is the rate of sea level rise accelerating?
The Future Climate Change Sea Level Rise page contains projections for future sea level rise.