Sea levels are already rising, and the rate is accelerating. In 2024, global sea levels rose 0.59 centimeters (about a quarter inch) in a single year, roughly 40% faster than the expected rate of 0.43 centimeters per year. The real question isn’t whether it will happen but how much and how fast, and the answer depends heavily on how much greenhouse gas the world continues to emit.
What’s Happening Right Now
Between 2002 and 2023, the Greenland and Antarctic ice sheets collectively lost enough ice to raise global sea levels by about 1.2 millimeters per year. Greenland alone shed roughly 270 billion tons of ice annually, contributing 0.8 millimeters per year. Antarctica added another 0.4 millimeters per year from approximately 150 billion tons of annual ice loss. On top of ice melt, ocean water expands as it warms, which accounts for a significant share of the total rise measured by satellites.
The 2024 spike caught researchers off guard. NASA’s analysis confirmed the rate of rise was nearly 6 millimeters that year, well above what models predicted. While a single year doesn’t establish a new trend, it fits a pattern of acceleration that has been building for decades.
The Next 30 Years
By 2050, global sea levels are projected to rise between 15 and 29 centimeters (roughly 6 to 11 inches) above the 1995-2014 baseline, depending on emissions. That range spans the best-case scenario, where emissions drop sharply, to the worst case, where fossil fuel use continues growing. The gap between those scenarios is surprisingly narrow at mid-century because much of the warming driving near-term rise is already locked in from past emissions.
For the U.S. specifically, the picture is more dramatic. Sea level along U.S. coastlines is expected to rise 10 to 12 inches (0.25 to 0.5 meters) in the next 30 years. That’s as much rise as the entire previous century produced, compressed into a single generation.
Starting in the mid-2030s, a natural lunar cycle that influences tides will align with these rising seas. A NASA-funded study found this combination will trigger a decade of rapidly increasing high-tide floods along every U.S. coast. The same lunar cycle exists now, but current sea levels are low enough that it causes only minor effects. By the mid-2030s, even a modest tidal boost on top of higher baseline seas will push water into streets far more often.
By 2100: Where Emissions Choices Matter Most
The projections for 2100 are where different emissions paths diverge sharply. Under the most optimistic scenario, with very low emissions, the median projection is 0.38 meters (about 15 inches) of total rise. Under an intermediate path, that climbs to 0.56 meters (22 inches). If emissions remain very high, the median hits 0.77 meters (about 2.5 feet), with the upper range reaching just over 1 meter (3.3 feet).
There’s also a “low confidence” high-emissions scenario that accounts for the possibility of rapid, unstable ice sheet collapse in Antarctica. If that process kicks in, sea levels could reach 1.6 meters (over 5 feet) by 2100. Scientists can’t yet say how likely this is, but they can’t rule it out either. The physics of massive ice sheets sliding into warmer ocean water remains one of the biggest uncertainties in climate science.
Why Your Location Changes the Number
Global averages obscure huge regional differences. The sea level rise you experience at a given coastline depends on several local factors that can make conditions much better or much worse than the global mean.
- Sinking land: When the ground beneath a coastal city drops, it has the same effect as the ocean rising. Natural processes like sediment compacting and tectonic shifts cause some land to sink, but so do human activities like pumping groundwater or extracting fossil fuels. Parts of the U.S. Gulf Coast and Southeast Asia are sinking fast enough to effectively double the rate of sea level rise they experience.
- Shifting ocean currents: Warmer water and freshwater from melting ice can alter ocean currents, changing how water piles up in certain regions. These shifts in temperature, salinity, and circulation can raise or lower local sea levels relative to the global trend.
- Gravitational effects from ice loss: This one is counterintuitive. Massive ice sheets exert a gravitational pull on surrounding ocean water. As they melt and lose mass, that pull weakens, and water actually migrates away from the melting ice toward the tropics and distant coastlines. Places close to Greenland may see less rise than average, while tropical and mid-latitude coasts see more.
What Flooding Will Look Like
The most immediate, tangible impact for most coastal residents isn’t permanent submersion. It’s nuisance flooding that becomes chronic. High-tide flooding, the kind that swamps low-lying roads and overwhelms storm drains on sunny days, is already breaking records along U.S. coasts. By 2050, many coastal communities can expect 25 to 75 days of high-tide flooding per year, up from just a handful today.
That shift changes daily life. It means roads regularly underwater during king tides, saltwater corroding infrastructure, and insurance costs climbing. It means businesses in flood-prone areas losing dozens of operating days annually. Long before the ocean permanently claims land, repeated flooding degrades property values, strains municipal budgets, and pushes people to relocate.
The timeline is not distant or hypothetical. The 2030s represent the first major inflection point, when lunar tidal cycles and rising baselines converge. The 2050s bring a new normal of frequent flooding in vulnerable areas. And by 2100, the choices made in the next two decades will determine whether coastal cities are managing a serious challenge or facing an existential one.