Extreme Weather Toolkit: Coastal Flooding

CM: National Sea Level Rise and Coastal Flooding 2023 (EN)

The frequency of coastal floods has risen sharply in recent decades. Rising sea levels due to human-caused warming will continue to increase both tidal flooding and flooding from extreme weather events in the years ahead.

The oceans have absorbed 90% of the extra heat caused by carbon pollution. As oceans heat up, the volume of seawater expands — causing sea levels to rise. Melting glaciers and ice sheets also contribute to rising sea levels.

Global mean sea level rose by nearly 8 inches from 1901 to 2018, according to the latest IPCC reports. Sea level rise has been accelerating since the late 1960s, and the rate of rise over the 2006-2018 period was nearly triple the average rate over the 1901-1990 time period. Studies indicate that roughly 70% of the observed rise since the 1970s is the result of human activity.

Sea level rise is accelerating along U.S. coasts. According to NOAA, sea levels along U.S. coasts are expected to rise as much over the next 30 years (10-12 inches, on average) as they did over the last 100 years.

As sea levels rise, flooding is becoming more common along U.S. coasts, where 40% of the population lives.

In our warming climate, it no longer takes a strong storm to flood streets, homes, businesses, and ecosystems along the coast. High tide flooding — also called nuisance flooding or sunny day flooding — is becoming more common in the U.S. The annual frequency of U.S. high tide flooding has more than doubled since 2000.

Sea levels are expected to continue rising with continued human emissions of carbon pollution. Coastal flood frequency is projected to more than triple by 2050 (relative to 2020) to reach a national average of 45 to 85 flood days per year.

According to Climate Central analysis, around 2.5 million Americans in 1.4 million homes live in areas at risk from a severe coastal flood in 2050 under projections that assume global pledged commitments to reduce carbon pollution are met.

Updated: May 2025