‘Moon wobble’, climate change to drive coastal flooding in 2030s


U.S. coastlines will face increased flooding in the mid-2030s thanks to a regular lunar cycle that will amplify sea-level rise caused by climate change, according to research led by NASA scientists.

A key factor identified by the scientists is a regular “wobble” in the moon’s orbit – first identified in the 18th century – that lasts 18.6 years. The moon’s gravitational pull helps control Earth’s tides.

During half of this lunar cycle, Earth’s regular daily tides are diminished, with lower than usual high tides and higher than usual low tides. In the other half of the cycle, the situation is reversed, with higher tides and lower tides.

The expected flooding results from the combination of continued sea level rise associated with climate change and the arrival of a strengthening part of the lunar cycle in the mid-2030s, the researchers said.

“In the background, we have long-term sea level rise associated with global warming. It’s causing sea levels to rise everywhere,” Ben Hamlington, NASA team leader and one of the study’s authors, told Reuters.

“This effect of the moon causes tides to vary, so we found that this effect is consistent with underlying sea level rise, and that will cause flooding specifically in this period from 2030 to 2040,” Hamlington said.

The researchers studied 89 tide gauge locations in all U.S. coastal states and territories except Alaska. The impact of the dynamics applies to the entire planet except for far northern coasts such as in Alaska.

The forecast pushes forward earlier estimates of serious coastal flooding by about 70 years.

The study, published this month in the journal Nature Climate Change, was led by members of a NASA science team that tracks sea level change. The study focused on U.S. coasts, but the findings are applicable to coasts worldwide, according to NASA.

“This is eye-opening for a lot of people,” Hamlington said. “It’s really critical information for planners. And I think there’s a lot of interest in getting this information from science and scientists into the hands of planners.”

Hamlington said city planners should plan accordingly.

“One building or a particular piece of infrastructure you may want to preserve for a very long time, while something else you may only want to protect or have available for a few years.”


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