Md. sea level to increase dramatically, report says

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Why did the crab cross the road? Because it could at high tide in Dorchester County. Bay Journal photo by Dave Harp

By Karl Blankenship

Bay Journal

A new report warns that Maryland will face a dramatic increase in the rate of sea level rise later this century, with nuisance flooding becoming a daily occurrence in many waterfront areas if nations fail to curb greenhouse gas emissions.

If emissions continue to rise, sea level in Maryland would likely increase 2.0 to 4.2 feet by 2100, which is two to four times the rate seen during the last century, according to the report from the University of Maryland Center for Environmental Science that was released in December. There is an outside chance the rise could exceed 5.2 feet, the report said.

If countries meet commitments in the 2015 Paris Climate Agreement, the sea level would still rise, but at a slower rate, with the likely increase ranging from 1.2 to 3.0 feet, with a 1-in-20 chance that the increase could exceed 3.7 feet.

“It actually has some good news and bad news,” said Donald Boesch, lead author of the report and former UMCES president. “The bad news is that there’s more evidence that unless we really limit warming to the Paris Agreement level… sea level rise could be higher than we thought. The good news is that if we’re on the emissions pathway that gets us to the Paris Agreement, it’s much more manageable.”

In any scenario, places along tidal waterways will become wetter. Nuisance flooding that occurred just a few times a year in places like the Annapolis city dock during the 1950s now takes place 40 or more days per year. Even under the best-case scenarios, according to the report, flooding there and in Baltimore’s Inner Harbor would become a near-daily occurrence. Meanwhile, storm surges during hurricanes would become much more dangerous.

The report, which is updated every five years, represents the consensus of an expert group of climate scientists from the mid-Atlantic region. It differs from the 2013 report by including alternative future scenarios based on whether nations successfully limit temperature increases to 2 degrees Celsius, as called for in the Paris agreement.

Through 2050, the report said, the most likely range of sea level rise in Maryland would be 0.8 to 1.6 feet (measured from a 2000 baseline), though there is a 5% chance of it exceeding 2 feet.

The extent to which emissions are reduced would begin to have a more pronounced impact in the second half of the century and become even greater after 2100, driven mostly by the loss of polar region ice, especially in Antarctica.

If no further actions are taken to curb global emissions through the end of this century, sea level rise in Maryland by 2150 would range from 3.4 to 6.6 feet, with a 1-in-20 chance it could exceed 8.5 feet.

If the Paris Agreement goals are met, the likely range of increase would be kept to 1.8 to 4.2 feet.

A major uncertainty is whether warmer temperatures could lead to the destabilization and more rapid loss of major ice sheets, in which case the amount of sea level rise in the state could be even greater, exceeding 20 feet in the next century, the report said. “Back at the beginning of the 20th century, more than 100 years ago, Greenland and Antarctica, were fairly stable,” Boesch said. “They were actually building ice. And now the evidence is pretty clear they’re losing ice. That process is just likely to accelerate, like literally a meltdown. How fast that meltdown will be depends on how much more warming there is.”