(Phys.org)—A team of researchers from across Europe has found evidence that suggests the rate of rise in sea levels from approximately 1902 until 1990 was less than other models have shown. This indicates, the team reports in their paper published in Proceedings of the National Academy of Sciences, that modern sea levels are rising faster than suspected.

Since approximately 1990, it has been relatively easy to measure sea level height across the planet because of advances in satellite technology. Prior to that time, as the researchers note, it was much more difficult due to a variety of factors such as gravity, land rising and sinking, wind patterns, etc., using tide gauges placed at sites around the world. In this new effort, the researchers have attempted to gain a better understanding of sea level changes during the 20th century prior to the use of satellite technology.

To create a better record, the researchers collected tide data and combined it with factors that are known to have caused changes in sea levels, such as shifts in land masses, regional events such as weather changes and, of course, runoff due to melting of glaciers and northern ice. They used all the data they had collected to create a model depicting sea levels in various parts of the world over the past 100 years, and then used the model to calculate the rate at which sea levels were rising on average over the same time frame. As expected, the model showed a rate of 3.1 millimeters per year since 1990, which agrees with satellite reports. But the model also showed that before 1990, the average rate was just 1.1 millimeter a year, which is significantly less than other models have shown. These numbers suggest that sea levels have been rising much faster since 1990 than other models have shown, in some cases up to three time faster.

The accelerated rise is believed to be due to more runoff from mountain glaciers, expansion of ocean waters due to warmer water temperatures, and melting of ice in the northern and southern parts of the planet—all due to global warming.

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