The last housing crisis wiped out billions of dollars in home equity and left millions of Americans underwater on their homes — owing more on their mortgages than their properties were worth. But while the real estate market has bounced back, rising sea levels in the coming decades could leave millions of homeowners underwater again — this time quite literally.

As the effects of climate change intensify, Boston and many other coastal communities in Massachusetts are particularly vulnerable. The City of Boston published a report last year detailing how the climate here is likely to change in the 21st century, and the forecast is troubling. High tides will get higher, waves may grow more forceful, and even weaker weather systems will produce damaging tidal surges — to say nothing of the havoc caused by more intense storms.

While long-term projections hinge heavily on future greenhouse gas reductions, even a drastic cut in carbon emissions would probably leave Boston Harbor at least 2 feet higher by the end of the century; assuming the status quo, we’re looking at up to 7 feet of sea level rise locally by 2100. (Regardless, a 1.5-foot increase seems likely by 2050.)

And though the report is specific to Boston’s future, the changes will affect communities all over the Commonwealth. Many more of us will be forced to get more familiar with the Federal Emergency Management Agency’s (FEMA) flood insurance program.