Sea level rise refers to the relatively recent net increase in Earth's ocean volume and depth, a trend that is widely attributed to rising global temperatures. While sea levels fluctuated dramatically in prehuman history, scientists link the past century's rapid rise at least partly to manmade global warming. 

 

Sea levels rose about 1.7 mm per year during the 20th century, according to the U.N. Intergovernmental Panel on Climate Change, and are now rising about 3.1 mm per year. This is partly because seawater naturally expands as it absorbs heat, increasing the overall oceanic volume, but also because excess warmth melts glaciers, sea ice, ice caps and ice sheets, adding more water to the oceans.

 

Sea level rise can have disastrous effects on the environment. As seawater washes inland, it erodes land, floods wetlands and damages habitats. As levels continue to rise, low-lying islands and coastlines will be vulnerable to flooding and eventually, submersion. (Photo: Wikimedia Commons)