Sea level rise, the rise of the oceans over time, has varied throughout Earth’s history but is now happening at an unprecedented rate. This is largely due to human-induced climate change, caused by the burning of fossil fuels and resulting increase in greenhouse gas emissions.
Rising seas pose a significant threat to coastal communities around the world, worsening flooding and erosion, increasing the intensity of storms, and making land and infrastructure vulnerable to damage. It also exacerbates poverty and inequality, particularly in poorer communities that are less able to adapt.
There are two main causes of sea level rise: melting glaciers and ice sheets add water to the ocean, and the volume of ocean waters increases as they warm up (thermal expansion). Melting from the Greenland and Antarctic ice sheets alone could raise global sea levels by 3 feet by 2100, according to NASA research.
In addition, the land is steadily rising in some places, such as the United States, because of natural geologic processes and human activities like pumping water out of aquifers. This is not directly related to sea level rise, but can cause local variations in tide-gauge based data.
Scientists measure sea level rise using a network of global tide-gauge stations and ocean sensors on satellites. The data reveal that sea levels have been rising rapidly since the start of the satellite record in 1993, but the rate has slowed over the past decade. These temporary shifts are due to complex, air-sea coupled processes like the El Nino Southern Oscillation.