An international research team found that some factors which cause sea-level rise were offset by dam building during the 20th century. They published their findings in Nature.

The Problem of Sea-Level Rise

Humans have always released massive amounts of carbon dioxide into our planet's atmosphere; it is so voluminous and is being released at such a rapid rate that global ambient temperatures have significantly risen for more than a century now.

Because of global warming, the water levels in our seas and oceans have continuously been rising from the increased melting of the polar glaciers and thermal water expansion, as water increases in volume when it becomes hotter. 

Discrepancy in Estimates

However, several recent scientific studies which have found some inconsistencies regarding the actual rise in the sea level as compared to the calculations of how much they should have increased. The latter is based on calculated figures and climate models.

The majority of researchers in the climate and related fields believe that the sea levels are supposed to be higher now than what their level is. We should have seen a more dramatic rise in sea levels in the last century.

The Study

In the new study, the research team took another look at the discrepancy and have suggested the possible reason for the difference.

Their answer: dams in reservoirs capture the differences in the water volume.

READ: Sea Level Rise Rapidly Occurring as Global Warming Melts Greenland Ice Sheets at Record Leve

The Methodology of the Study

The research team collected datasets from other researches which described climate change, sea levels, and glacial melting since the year 1900. These data were then utilized to make new climate models that show sea level rise based on the rate of global warming from the year 1900 to 2018.

Afterward, the team made calculations of the estimated average rate of the rise in sea levels.

Results of the Study

For the whole period considered in the study, they arrived at the estimated figure of 1.56 +/- 0.330 millimeters each year. Meanwhile, the actual change in the sea level for this period has been measured to be 1.52 +/- 0.330 millimeters each year. The estimate and the real rise in sea level now approximate each other more closely. 

The research team then determined the various factors and causes which contributed to the rise in sea level worldwide. According to their study results, the dams that were built in the past century have had a beneficial effect in mitigating sea level rise.

READ ALSO: New Study Shows Sea Level Rise Will Devastate Cities in California 

A More Accurate Estimate Due to the Dams

They arrived at a much closer figure to the actual levels than past studies because they considered the volumes of glacier water that were confined to the reservoirs due to the presence of dams. These vast amounts of stored water were prevented from contributing to the total volume of the oceans.

Some of the other findings that the study uncovered involve the relative consistency in sea level rise, with two significant exceptions. The first was in the 1940s, in which the rate in growth was faster for several years; the second was in the 1970s, in which the rise slowed. The slowing in the latter period was considered to be due to the several dams that were built.

Finally, the team noted that sea-level rise had had a more consistent and faster and rate starting in the 1990s when dam building drastically slowed.

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