The European Union’s Copernicus Atmosphere Monitoring Service said Thursday that the ozone hole, which appears every year during the Southern Hemisphere spring, has grown considerably in the past week following an average start.

“Forecasts show that this year’s hole has evolved into a rather than usual one,” said Vincent-Henri Peuch, who heads the EU’s satellite monitoring service. “We are looking at a quite big and potentially also deep ozone hole.”

Atmospheric ozone absorbs ultraviolet light coming from the sun. Its absence means more of this high-energy radiation reaches Earth, where it can harm living cells.

Peuch noted that last year’s ozone hole also started out unremarkably but then turned into one of the longest-lasting ones on record.

The Montreal Protocol, signed in 1987, led to a ban on a group of chemicals called halocarbons that were blamed for exacerbating the annual ozone hole.

A key factor identified by the scientists is a regular “wobble” in the moon’s orbit first identified in the 18^th century – that takes 18.6 years to complete. The moon’s gravitational pull helps drive Earth’s tides.

In half of the lunar cycle, Earth’s regular daily tides are diminished, with high tides lower than usual and low tides higher than usual. In the cycle’s other half, the situation is reversed, with high tides higher and low tide lower.

The expected flooding will result from the combination of continuing sea level rise associated with climate change and the arrival of an amplification part of the lunar cycle in the mid-2030s, the researchers said.

“In the background, we have long-term sea level rise associated with global warming. It’s causing sea level to increase everywhere,” Ban Hamlington, NASA team leader and one of the study’s authors, told Reuters.

“The effect from the moon caused the tides to vary, so what we found is that this effect lines up with the underlying sea level rise, and that will cause flooding specifically in that time period from 2030 to 2040,” Hamlington said.