Local scientists and climate activists have dubbed this week’s phenomenon a “massive flood,” partly to distinguish it from the better-known “king tides” that typically occur during full and new moons. (There is no scientific definition for a “king tide”).

This is even higher with wicked high tides. They are technically called perigean spring tides and occur when there is a new or full moon and the moon is very close to the earth at the same time.

This week’s extreme flooding offers a glimpse into the future: It shows sea levels comparable to the everyday heights that climate scientists predict the average in Boston will reach in the coming decades due to climate change.

In Boston, sea levels will most likely rise by about a foot by 2050 compared to 2000, climate scientists have found, and another foot could be added in the decades after that.

Perigean spring tides occur about eight times a year, but the planets are only “one piece of the puzzle” of very high water levels, says Greg Dusek, an oceanographer with the National Oceanic and Atmospheric Administration. Seasonal trends can also bring higher tides; high water temperatures in late summer and early fall, for example, cause water molecules to expand.

“That’s when sea temperatures (on the east coast) are at their highest,” Dusek said.

This means that a spring tide in September results in higher tides than a spring tide.

Location also plays a role. Boston has a very large tidal range, meaning fluctuating tides are easy to notice here compared to the Gulf Coast of Florida, for example, Dusek said.

“In places with larger tidal ranges, this cycle also tends to be more affected because the tides have a much greater influence on water level fluctuations near the coast,” Dusek said.

Sea level is not a static number. It can fluctuate over months or years depending on water temperature, wind strength, lunar cycles, and more. However, scientists have found that the long-term trend of sea level rise in modern times is primarily caused by climate change. Glaciers and sea ice are melting and ocean temperatures are rising, causing the water to expand.

According to data from a tide gauge in Fort Point Channel, the average sea level in Boston is now more than a foot higher than it was in the 1920s, making the last decade the period with the highest sea levels in Boston since modern weather records began.

In New England, sea level rise tends to be greater than the global average, partly because the land here is slowly subsiding due to the effects of ancient glaciers.

Sea level rise projections for Boston after mid-century vary depending on whether humans release fewer planet-warming greenhouse gases into the atmosphere. But even conservative estimates suggest sea levels will rise by about two feet over the next 50 years, according to a 2022 report on the impacts of climate change on Boston.

Perhaps even more worrying is the pace at which this rise is occurring: between 2001 and 2019, sea levels rose twice as fast as in the last century.

Towards the end of this decade, a 19-year natural lunar cycle begins, increasing Boston’s tidal range and further increasing the risk of flooding.

According to NOAA, another perigean spring tide is expected in mid-October, likely raising water levels in Boston to nearly 12 feet.

Erin Douglas can be reached at [email protected]. Follow her @erinmdouglas23.