Tipping Point Nears for ‘Emerging Flooding Crisis’

Soggy times are coming for cities along both U.S. coasts and they’ll be here much quicker than previously thought.  By mid-century, sea level rise is set to make floods a monthly occurrence in more than two dozen major cities, and in some of those cities, it could become a daily occurrence by the 2070s.

The watery findings come from a new study published Thursday and presented at the American Geophysical Union meeting.  It builds on findings earlier this year from National Oceanic and Atmospheric Administration (NOAA) scientists that show sea level rise tipping points are just a few decades away for the majority of the cities they looked at.
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And while the onset of the crisis has been gradual, it’s likely to reach a tipping point in the 2050s for all 26 cities that Sweet examined, after which point the risk of flooding increases dramatically.  Sweet defined a tipping point as the time when a city would experience 30 days of nuisance flooding — floods roughly up to 20 inches above the high-tide mark — per year.

While most cities will reach that tipping point around 2050 unless greenhouse gas emissions are slowed, a number of locations will cross that line much sooner.  Boston has nearly crossed that mark already, and New York and Philadelphia are likely to reach the 30-day flood threshold at some point in the 2020s.

Reaching those levels is a near guarantee due to the sea level rise already locked in. After that, the world’s choice on when or if to reduce greenhouse emissions will determine just how regular future flooding will be.  In cities such as Norfolk and San Francisco, it will become a daily problem by the 2070s on the current emissions pathway, at which points seas could be up to 4 feet higher, according to recent climate projections.

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