Sea level rise—the gradual increase of ocean waters that happens as Earth warms—is the clearest and most visible consequence of climate change. It’s a topic that has been in the news for years and that is often the subject of science fiction movies, featuring images like people clinging to ramshackle floats or New York City’s Statue of Liberty teetering above the waterline.
Scientists measure changes in sea level at a range of scales, from global to local. They use direct measurements of glacier or ice sheet melt rates, ocean temperature and circulation data, as well as satellite laser altimeter readings that measure tiny shifts in gravity over the oceans when water shifts from land to the ocean. These measurements allow scientists to estimate how much water has moved into the oceans and to adjust their global projections for coastal conditions.
Local changes in sea levels are caused by a variety of factors, including regular daily tides and natural year-to-year fluctuations from events like El Nino. Those temporary ups and downs add to the overall rate of sea level rise in a particular area.
The sea level rise resulting from human-caused climate change is expected to continue at its current rate, which is more than twice the rate of the last century. That will increase the risk of flooding and erosion for coastal communities and will likely lead to widespread relocations. Communities can take multiple strategies to adapt to sea level rise, including “hard” approaches such as beach nourishment and dune rehabilitation, as well as “soft” adaptations like community planning and preparedness measures.