Rising Levels

The Intergovernmental Panel on Climate Change’s 2013 report states that “each of the last three decades have been successively warmer at the Earth’s surface than any preceding decade since 1850.” As a result the Greenland and Antarctic ice sheets have been losing mass and glaciers have continued to shrink almost worldwide. We can see the impacts of the melting glaciers in the rising levels of our oceans. In addition, “as the global ocean will continue to warm during the 21st century, heat will penetrate from the surface to the deep ocean and affect the ocean circulation” and expansion, which means sea level will continue to rise even more. “The rate of sea level rise since the mid 19th century has been larger than the mean rate during the previous two millennia.” Current sea level rise is about 3 mm/year worldwide.

On one hand, this constant and relatively rapid rise in sea level has huge influence on human population in coastal areas. On the other hand, human population has a huge influence on the extent of sea level rise. First of all human activities, such as burning fossil fuels to produce energy, release greenhouse gases (such as Carbon Dioxide to Methane) into the atmosphere, which “act like a blanket around Earth, trapping energy in the atmosphere and causing it to warm” (EPA). Second various human activities increases coastal subsidence, which in turn increases sea level rising. Land subsidence is “the sinking of land and\or the removal of liquids from the ground.” While subsidence are naturally occurring different human activities such as oil, gas and groundwater mining usually result in ten times more rapid sinking of the land. In coastal locations where land is sinking faster the relative sea level will rise higher. According to New Scientist Magazine December 2012 article, “2/3 of the world major river deltas are subsiding.”

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Photo from the New Scientist Magazine.

Finally human change of wetlands also influences the extent of sea level rise. Different human activities reduce or eliminate sediment transport needed for deltas and result in wetland loss. Among those activities is sediment retention behind dams, extraction of freshwater, stabilization of banks and land reclamation. One of the major examples of the impact of wetlands loss on the extent of sea level is found in Louisiana. According to Losing Ground website “in just 80 years, about 2,000 square miles of Louisiana coastal landscape have turned to open water, wiping places off maps, bringing the Gulf of Mexico to the back door of New Orleans and posing a lethal threat to an energy and shipping corridor vital to the nation’s economy.”

As seen in the interactive satellite images of coastal Louisiana on the website, there is an extent of historical wetland loss in the area.

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Louisiana coastline in 1922. Photo from Losing Ground Website.
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Louisiana coastline in 2014. Photo from Losing Ground Website.

At the current rates in which sea level is rising and land is sinking the Gulf of Mexico could rise as much as 4.3 feet across this landscape, by 2100. If that happens most of Southeast Louisiana will be underwater, and about 2 million people would need to find other places to live.

With half of the world’s population living within 60 km of the sea, and three-quarters of all large cities are located on the coast it is clear we need to adapt [1].

“Either we can grow gills, or we’ll need to think of other ways of adapting”           Boris Johnson, Mayor of London

Today about 20% of cities around the globe have developed adaptation strategies, and New York City is one of them. Mayor Bloomberg lunched the “A Stronger, More Resilient New York” program, in June 2013, as a response to Hurricane Sandy that hit the city in October 2012.

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Flood Zones in NYC.

According to Inside the Climate News, “New York City’s $19.5 billion plan to adapt to climate change is based on hyper-local climate models specific to New York and includes more than 250 initiatives to reduce the city’s vulnerability to coastal flooding and storm surge. 80% of the plan founds are devoted for repairing and improving current infrastructure and 20% are devoted for developing coastal defense.”

Sea level rising is not just a problem that will affect future generations. It is a current and immediate problem that is already affecting people leaving by coastlines across the glob. As London’s mayor said we need to adapt, but that adaptation shouldn’t only include improving infrastructure and developing coastal defense systems, it should also include a deeper change in all the human activities that increase the extent of sea level rising. We need to reduce our greenhouse gases emissions, to stop oil, gas and groundwater mining and to restore wetlands. Otherwise we better start growing gills.


[1] Based on The United Nations Environment Program (UNEP) data.