The following graph was downloaded from the EPA’s Climate Change Indicators: Sea Level page. I then fit a straight line to the data using the GNU image manipulation program (the GIMP). Take a look:
Between 1880 and 1960, the data is a fair approximation to a straight line, indicating a slow natural rise in sea level of about one inch every twenty years. If the sea level were to continue to rise at that rate, there would be an increase of about 4 inches (10 cm) by the end of the century.
Unfortunately, the data show that sea level rise is accelerating. By 2015, the most recent year for which we have data, sea level appears to have risen by about 2 inches more than the decade long trend would have predicted. In the first 15 years of this century, sea level has risen by roughly 2 inches. Assuming that sea level rise doesn’t accelerate further, this rate of increase would lead to about 8 inches (20 cm) of increase by the end of the century.
The NOAA report Global and Regional Sea Level Rise Scenarios predicts (based on climate models) that sea levels will rise between 30 cm (1 foot) and 2.5 m (8′ 4″). The intermediate prediction is 1m (3′ 4″). This is more than four times the trend over the last 15 years.
With the Global Sea Level Rise Map, you can view a map of any part of the world and see what would happen if the sea level increased (in 1m increments). For example, here’s Bangladesh (one of the lowest lying countries) now and with 1m higher sea levels:
While this doesn’t look a whole lot different, you can see incursions along the banks of the Padma and Meghna rivers. These would inundate the homes of thousands of the poorest people in the world. In Canada, we have the resources to prepare dykes and pumping stations. The Bangladeshi’s do not. The country’s climate scientists believe that by 2050, rising sea levels will inundate 17 percent of the land and displace about 18 million people.