It could be time to sound the alarm, as a new study reveals that the rise in global sea levels from the end of the 20th century until the last two decades is accelerating much faster than scientists previously believed. It was discovered that there were loopholes in the estimates made for an earlier period which has caused the rest of the readings to be off.
For the new study published this week in the journal Nature, lead researcher Carling Hay from Harvard's Department of Earth & Planetary Sciences and colleagues reported that the rise of global sea levels in the 20th century was not quite as high as previously estimated.
Prior research had determined that sea levels had risen about six inches during the 20th century. However, the researchers determined that the rise in sea level during this period was in fact only about five inches. Since the estimates in the 1990s were accurate, it means that the rise in sea levels over the past several decades has been higher than previously believed.
Before the 1990s, satellites were not yet in use and estimates of sea levels depended on the records of the tide gauges, which are not evenly distributed around the world. From these records, researchers have estimated that the sea level rose in the 20th century at a rate of 1.6 to 1.9 millimeters annually. But, there are limits to these methods.
"But these simple averages aren't representative of a true global mean value," Hay says. "Tide gauges are located along coasts, therefore, large areas of the ocean aren't being included in these estimates. And the records that do exist commonly have large gaps."
Over the last couple of decades, satellites have been used to record measurements with much greater accuracy, revealing that the sea level rise has been approximately 3 millimeters per year.
"Our estimates from 1993 to 2010 agree with [the prior] estimates from modern tide gauges and satellite altimetry, within the bounds of uncertainty. But that means that the acceleration into the last two decades is far worse than previously thought," Hay says.
According to the study, the rate of sea level rises is about 25 percent higher when compared with previous estimates, and the accelerated rate can be blamed on the melting ice sheets in West Antarctica and Greenland, as well as, the shrinking of glaciers. These phenomena are thought to be attributed to man-made global warming.
Researchers believe that once the study results have been validated, it could solve some discrepancies in the estimates of global sea level rise.
