A NASA study recently revealed that, on average, sea levels around the world have risen almost 3 inches in less than 25 years, and that, in some areas levels have actually risen 9 inches. NASA is currently in the midst of an intensive study, using observations and analysis, all of which are pointing in one direction: an unavoidable rise in sea levels of several feet over the next hundred years.
University of Colorado, Boulder’s Steve Nerem is the lead of the Sea Level Change Team. “Given what we know now about how the ocean expands as it warms,” says Nerem, “and how ice sheets and glaciers are adding water to the seas, it’s pretty certain we are locked into at least 3 feet of sea level rise, and probably more.” But, he adds, “…we don't know whether it will happen within a century or somewhat longer,” Nerem explains.
The NASA team just released their new forecasts based on analysis of the past 23 years of their sea level data. This is how long NASA has been keeping satellite records on sea levels.
The data is from three satellite missions. The first mission, launched in 1992, was a collaboration between NASA and the Centre National d'Études Spatiales, or the CNES, the French space agency. The second was a mission called Jason-3, which was led by the NOAA, the National Oceanic and Atmospheric Administration. Other participants included NASA, CNES and the European Organisation for the Exploitation of Meteorological Satellites.
The United Nations Intergovernmental Panel on Climate Change (or the IPCC) issued an assessment in 2013, which was based on a consensus of international researchers. It stated that global sea levels would likely rise from 1 to 3 feet by the end of the century. Nerem’s team has found, in their analysis of data that has become available since the IPCC’s 2013 report, that three feet is much more likely, and that, in that time, sea levels could rise even more.
One surprising finding from Nerem’s team’s analysis is that changes in sea level are not uniform world-wide. Ocean currents and natural cycles such as the Pacific Decadal Oscillation (or the PDO) cause some significant regional differences. But, they are all subject to change as these natural cycles wax and wane, which could cause problems in the future.
“Sea level along the west coast of the United States has actually fallen over the past 20 years,” says Josh Willis, an oceanographer at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, “…long-term natural cycles there are hiding the impact of global warming. However,” he explains, “there are signs this pattern is changing. We can expect accelerated rates of sea level rise along this coast over the next decade as the region recovers from its temporary sea level ‘deficit.’”