Alert! Sea level is rapidly rising, and a volcanic eruption that happened decades ago could hold the clue to what's actually happening.

Since 1993, scientists have observed an annual steady rise of three-millimeter on sea level. Scientists predict that the amount of sea level should increase per year because water expands. However, since 1993, experts observe a steady sea level rise at 3.5 millimeters per year (1.4 inches per decade).

This constant rise has been perplexing scientists for years, but now, a recent study has revealed the reason behind it -- the 1991 Mount Pinatubo volcanic eruption in the Philippines.

According to the study published in the journal Nature, the eruption, which is considered the largest eruption in the late 20th century, hid clues of climate change by briefly cooling the oceans; thus, the steady rate of sea level rise since 1993.

Today, lead study author John Fasullo and his team of researchers claim that sea levels are escalating more than expected due to the long pause caused by the eruption.

“We got a very biased view of sea level rise, based on the happenstance timing of the launch of [the first] altimeter satellites,” Fasullo told Gizmodo.

The study says that rising of the global mean sea level is the most powerful indicator of climate change.

To analyze how Mount Pinatubo affected the global sea level, the researchers created model simulations and applied natural factors to them for observation.

Results showed that aerosols from the volcanic eruption blocked sunlight, resulting to cooler seas, which, as Fasullo says, "skewed our impression of acceleration."

Fasullo notes that they are expecting an acceleration in global warming in the next to 10 years.

“Those effects largely have ebbed by now, and once we get a few more years into the altimeter record, we should see a clear acceleration. That’s really the punch line of the article," he said via Washington Post.