Sea Level Rise: How fast, what happens, why?


Warming of the global climate results in sea level rise for a variety of reasons. The global climate is warming due to the "greenhouse effect". Most of our sun's radiation is visible light, which passes through the atmosphere largely unaffected. The radiation warms the Earth's surface, which then radiates the heat as infrared radiation. But water vapor, atmospheric carbon dioxide (CO2), and some other atmospheric gases absorb the infrared radiation, rather than letting it radiate out into space. This results in a warming of the Earth's atmosphere. Because glass in a greenhouse does essentially the same thing, this phenomenon is known as the greenhouse effect. Without the greenhouse effect, the Earth would be 33oC (60oF) cooler. But because of the burning of fossil fuels (coal, oil, and gas) more CO2 and other gases are being released into the atmosphere and thus causing a warming of the global climate. 

This warming of the climate causes several changes that affect sea levels. First, the Antarctic ice sheet is thinning, adding more water to the oceans. At the same time, the ocean water is becoming warmer, which results in a slight expansion of the water, raising sea level. Also, mountain glaciers are melting. 

Scientists do not agree on all of the effects the global warming will cause. Some feel warmer temperatures will result in more water evaporation, resulting in more cloud cover, which will help to lower temperatures. Others feel the increase in evaporation will not be enough to increase the cloud cover, only enough to increase the greenhouse effect, raising temperatures even more. 

Higher temperatures will result in less snow and ice cover. These light surfaces reflect sunlight back into space. Without the snow and ice cover, more light will be absorbed, resulting in more warming of the Earth. 

The table below lists a range of estimates for sea level rise for the next 100 years.


Table 1.1. Worldwide Sea Level Rise Scenarios, 2000 - 2100 (in cm and ft above 2000 levels)








8.2 (.27)

19.0 (.62)

33.2 (1.04)

51.4 (1.64)

Mid-range low

17.4 (.57)

43.5 (1.41)

82.4 (2.71)

135.6 (4.41)

Mid-range high

26.1 (.87)

65.4 (2.17)

123.6 (4.07)

203.4 (6.67)


37.8 (1.24)

99.6 (3.24)

195.6 (6.44)

327.9 (10.74)



  1. Measure the height of the top of the split rock above sea level, using the rack line as zero sea level.

Split Rock



 Figure 1. Split Rock at Bluff Point State Park




  1. Using the above table, how many feet of the rock will be under water in 2100? Calculate the most and least conservative inundations.
  1. Graph the sea level changes from the above table, using the foot measurements and the highest rate. Using your graph line, project how long it will take for split rock to be completely covered with water.
  1. Looking at the map below, determine when the Groton - New London airport runways will be mostly under water, using the highest rate of sea level rise.

map of Grouton-New London Airport


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