Sea levels around the world are rising because of climate change. As humans burn fossil fuels, we release carbon dioxide and other greenhouse gas emissions, which warm the Earth and the oceans. Because water expands as it warms, the oceans are rising higher as they heat up. Climate change is also melting glaciers and ice sheets, adding more water to the oceans.

Worldwide, sea levels have gone up roughly eight to nine inches in the last century, and sea levels in some places have gone up much more than that (1). In the past two decades, sea level rise has been speeding up as more ice and glaciers melt (2).

Even if humans significantly cut greenhouse gas emissions, we can still expect one to two feet of additional sea level rise by the end of the century because of past emissions (3). But to a certain extent, how much the sea level continues to rise beyond that is up to us—and how much we keep burning fossil fuels.

The rate of sea level rise in a particular place depends on a number of factors, including ocean currents, the movement of the Earth’s crust, and whether coastal land is rising or sinking. The eastern United States is one example of a sea level rise hot spot, where the ocean along some coastal cities is already a foot and a half higher than it was before the industrial revolution (4).

We can already see how sea level rise is affecting coastal areas. For example, cities like Norfolk, Virginia and Venice are seeing many more high tide (or “sunny day”) floods, which damage roads, sewer systems and other infrastructure, than they used to (5,6).

Sea level rise is also making hurricanes and other storms more damaging—and more deadly. The high winds from hurricanes push a wall of water, known as a “storm surge,” toward shore. Sea level rise gives those waves a head start, propelling them further inland.

Scientists warn that, depending on how much sea levels continue to rise, certain islands and coastal cities could go underwater. This is especially concerning because over 10% of the world’s population lives in coastal areas that are less than ten meters (about 33 feet) above sea level (7)—meaning sea level rise could displace tens to hundreds of millions of people. Sea level rise also threatens to flood large areas of farmland in countries like Bangladesh, Vietnam and Egypt, and make freshwater in some areas too salty to drink.

If sea levels rise a little bit, people living in some coastal areas can, to a certain extent, adapt. Some coastal communities are doing this by building or fortifying sea walls or seawater pumping systems, and raising roads and other critical infrastructure. Coastal regions can also restore wetlands and other coastal ecosystems that act as natural storm buffers, and limit new development in at-risk areas.

But sea level rise, combined with worsening storms and erosion, has already rendered certain coastal areas uninhabitable. The southwestern Louisiana peninsula of Isle de Jean Charles is one such place, where community leaders are working to resettle residents inland (8).

As sea levels continue to rise, coastal communities around the world will likely face similar hard choices. Experts are concerned that poorer communities, or poorer people living within wealthier areas, will not have the money and other resources needed to safely relocate. That’s why leaders from some of these areas, like the island nation of Kiribati, argue that wealthier nations that are most responsible for causing climate change should help fund the resettlement of people pushed from their homes by sea level rise.

Published May 25, 2021.

Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International license (CC BY-NC-SA 4.0).

Photo Credit: Jonathan Ford via Unsplash

FOOTNOTES

1 Lindsay, Rebecca. “Climate Change: Global Sea Level.” National Oceanic and Atmospheric Administration, climate.gov, 25 Jan. 2021.

2 U.S. Environmental Protection Agency. “Climate Change Indicators: Sea Level.” 27 Apr. 2021.

3 Intergovernmental Panel on Climate Change: Special Report on the Ocean and Cryosphere in a Changing Climate, Summary for Policymakers.

4 "Why Is Sea Level Rising Faster in Some Places Along the U.S. East Coast Than Others?" Woods Hole Oceanographic Institute, 19 Dec. 2018.

5 Dahl, Kristina A., et al. “Sea Level Rise Drives Increased Tidal Flooding Frequency at Tide Gauges along the U.S. East and Gulf Coasts: Projections for 2030 and 2045.” PLOS ONE, vol. 12, no. 2, 2017, doi:10.1371/journal.pone.0170949.

6 Cavaleri, Luigi, et al. “The 2019 Flooding of Venice and Its Implications for Future Predictions.” Oceanography, vol. 33, no. 1, 4 Mar. 2020, doi:10.5670/oceanog.2020.105

7 Kulp, Scott A., and Benjamin H. Strauss. “New Elevation Data Triple Estimates of Global Vulnerability to Sea-Level Rise and Coastal Flooding.” Nature Communications, vol. 10, no. 1, 2019, doi:10.1038/s41467-019-12808-z.

8 Jessee, Nathan. “Community Resettlement in Louisiana: Learning from Histories of Horror and Hope.” Louisiana's Response to Extreme Weather, 2019, pp. 147–184., doi:10.1007/978-3-030-27205-0_6.