The Basics | Global Sea Level Rise – U.S. Sea Level Change

Key Takeaways

Greenhouse gases added to the atmosphere by human activities are warming the planet.
Global sea level is rising mainly from ocean warming and melting land ice due to climate change.
Global sea level is rising faster today than it was 100 years ago.

The Link to Climate ChangeGlobal Sea Level Rise Is Linked to Climate Change

For over 100 years, humans have burned coal, gas, and oil to produce energy. Burning these fossil fuels releases greenhouse gases into the air. Greenhouse gases warm the Earth, like a blanket wrapped around the globe. Adding more greenhouse gases thickens the blanket and the Earth becomes warmer.

Around 90% of this added heat is being absorbed by the ocean, warming it up. When water warms, it expands and takes up more space. This causes the water to rise along the coastline. Currently, about one third (around 33%) of global sea level rise is because of ocean warming.

The other two thirds (around 66%) of global sea level rise is because of melting land ice. As Earth heats up, it melts the land ice, including the Greenland and Antarctic Ice Sheets and other mountain glaciers. The water then flows into the ocean which raises sea levels.

Infographic showing causes of global sea level rise: greenhouse gases added by human activities, which warms the planet, leading to ocean warming and land ice melting — Greenhouse gas emissions lead to warming of Earth's atmosphere and ocean. This warming leads to increases in ice sheet and glacier melting, as well as ocean expansion. As the ocean takes up more space due to warming and gains mass from formerly frozen ice, the global sea level rises. As greenhouse gas emissions continue, global sea level rises faster over time.Click to enlarge. Credit: Allie Braun, NASA JPL.

Sea Level Snippets

The ocean absorbs about 90% of the excess heat from global warming. To give you an idea of how much heat that is, imagine every person on Earth (around 8 billion people) using 100 hair dryers at the same time and pointing them at the ocean. That's roughly the amount of heat the ocean is absorbing every second!
The amount of ice being lost from Greenland and Antarctic ice sheets each year is roughly equivalent to covering New York City in a layer of ice that is 1250 feet (381 meters) thick, which is about the same height as the Empire State Building.

How Do We Know Sea Level Rise Is Increasing?How Do We Know Sea Levels Are Rising Faster Than They Were Before?

For decades, sea levels have been measured across the world with tide gauges and satellite altimeters. These measurements are combined to calculate the average ocean height across the world, the global sea level, each month or year. Comparing these values over time shows the amount and rate of change of global sea level.

The global sea level has been rising since the 19th century, when modern records began. And, it has been rising faster in recent years. It took 90 years (1902 – 1992) for the global sea level to rise around 4 inches. In just the last 30 years (1993 - 2023), that same amount of rise, around 4 inches, happened again.

When we plot global sea level it is not a straight line, but rather it goes up and down slightly. These movements, known as variability, show natural changes that happen due to a number of different factors. Things like tides can change sea levels over hours or days. Large climate events, like El Niño, can cause changes in sea levels over months or years. However, even though we see wiggles up and down in the global sea level, these natural changes are not large enough to offset the overall rise in global sea level we are seeing from climate change.

Dive Deeper: Learn more about global sea level rise and why it is happening.

Next: Local Sea Level Change

Sea Level 101

Why is Global Sea Level Rising?

The Link to Climate ChangeGlobal Sea Level Rise Is Linked to Climate Change

How Do We Know Sea Level Rise Is Increasing?How Do We Know Sea Levels Are Rising Faster Than They Were Before?