Two megacities are sinking beneath the waves as global sea levels rise even higher.

For years, scientists have been warning about the climate crisis looming over the planet: Earth is losing its ice sheets, and heatwaves and droughts are becoming increasingly severe. Researchers also predict that soon the global sea level will rise significantly, putting coastal communities at risk, as reported by Live Science.

A study conducted by NASA and NOAA revealed that certain areas of California are sinking, meaning that the anticipated sea level rise for parts of Los Angeles and San Francisco has doubled. Scientists now believe that the sea level in these regions may rise more than twice as much as previously forecasted.

The study's authors reached this conclusion after analyzing land elevation along the California coastline using satellite radar. Statistics indicate that in "hot spots" like San Rafael and Foster City in the San Francisco Bay area, land is sinking by more than 10 millimeters per year. This subsidence suggests that sea levels in the region could rise by over 45 centimeters in the next 25 years—more than double the previous regional estimate of 19 centimeters.

The findings suggest that similar processes in the Los Angeles area will add an additional 15 centimeters to the projected 17-centimeter sea level rise by mid-century. According to the lead author of the study, Marin Govorchin, a remote sensing scientist at NASA's Jet Propulsion Laboratory, in many parts of the world, land is sinking faster than the sea is rising—complicating the situation.

Land uplift and subsidence, also known as "vertical land movements," are caused by natural processes such as tectonic plate movements, as well as human factors like groundwater extraction.

Globally, sea levels are rising alongside climate change. The additional heat from the warming planet melts glaciers and ice sheets and expands water in the oceans. All of this ultimately pushes coastlines further inland, and scientists are concerned that rising sea levels pose a threat to coastal communities worldwide.

In this new study, researchers aimed to understand how vertical land movement affects this process. They utilized radar data collected by the European Space Agency's Sentinel-1 satellites, as well as land movement data obtained through the Global Navigation Satellite System.

The results indicate that the most extreme subsidence occurred in central California, where aggressive groundwater extraction is causing parts of the Central Valley to sink by 20 centimeters annually. However, the data also suggest that subsidence is not occurring uniformly across all areas.

The danger lies in the fact that vertical land movement is difficult to predict, but the results indicate that it is an important factor that should be considered in forecasts about which areas will soon be submerged.