For most of the last century, thermal expansion from simply heating up the ocean was the main contributor to the global rise in sea level. But that’s changed in the last two decades.

A recent study shows melting of land-based ice and the resulting runoff into the sea now accounts for twice as much sea level rise as thermal expansion does. More than half of the contribution from land-based ice is from melting of alpine glaciers and ice caps, while Greenland and Antarctica (both ice sheets) account for the rest.

Flooding during high tides—something that rarely occurred in the past—is now common in some places and is projected to grow to the point that sections of coastal cities may flood so often they would become unusable in the near future, according to a report the Union of Concerned Scientists (UCS) released today, “Encroaching Tides: How Sea Level Rise and Tidal Flooding Threaten U.S. East and Gulf Coast Communities over the Next 30 Years.”

Flooding during high tides—something that rarely occurred in the past—is now common in some places and is projected to grow to the point that sections of coastal cities may flood so often they would become unusable in the near future, according to a report the Union of Concerned Scientists (UCS) released today, “Encroaching Tides: How Sea Level Rise and Tidal Flooding Threaten U.S. East and Gulf Coast Communities over the Next 30 Years.”

Climate Facts

Union of Concerned Scientists


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