At the end of the century, when a rapidly warming Casco Bay is predicted to have risen another 4 feet because of climate change, a big storm that blows in hard from the southeast on a new moon tide – like the one that hit us on Jan. 10 – could spell disaster for Portland.

Much of Commercial Street, which was built on filled land, would be overrun by up to 10 feet of water, along with its shops, bars and restaurants beloved by locals and tourists, as would the working waterfront that serves the area’s lobster and fishing fleet.

Mercy Hospital, the old B&M bean factory, the East Deering and Bayside neighborhoods – all flooded.

According to Maine Climate Council figures, the area that would be lost to sea level rise, a new moon tide, and the extra 5 or so feet of storm surge that comes along with a 1% annual chance storm generates $1.5 billion of the city’s current gross domestic product and more than 16,500 jobs.

And that’s without waves, which are notoriously hard to predict. And whether we manage to rein in global emissions. City officials note that floodwaters have rarely crossed Commercial Street. But if the world keeps on burning fossil fuels at the rate we are now, an extra 5 feet of sea level rise could change all that.