New satellite research from NASA shows that not only are global sea levels rising quickly, but they could rise even more drastically than previous reports estimated. According to the US space agency, seas around the world have risen an average of three inches (7.6 cm) since 1992, and as much as nine inches (23 cm) in certain places.
“It’s pretty certain we are locked into at least 3 feet of sea level rise, and probably more,” said Steve Nerem, head of NASA’s Sea Level Change Team. “But we don’t know whether it will happen within a century or somewhat longer.”
Sea levels are rising for three main reasons: The melting of ice sheets in Greenland and Antarctica, the melting of mountain glaciers, and the expansion of oceans as they absorb heat and become warmer. All three causes can be directly attributed to global warming.
The United Nations Intergovernmental Panel on Climate Change (IPCC) said in 2013 that global sea levels were likely to rise between one and three feet over the next century. But after studying 23 years of satellite information—the entire record of data available—NASA warns that those estimates are probably too conservative.
“The data shows that sea level is rising faster than it was 50 years ago, and it’s very likely to get worse in the future,” Nerem said. The question now, NASA says, is “how that range might shift upward.”
This NASA visualization shows how much the Greenland ice sheet has melted over the last decade:
“The Greenland ice sheet, covering 660,000 square miles—nearly the area of Alaska—shed an average of 303 gigatons of ice a year over the past decade, according to satellite measurements,” NASA said. “The Antarctic ice sheet, covering 5.4 million square miles—larger than the United States and India combined—has lost an average of 118 gigatons a year.
All that melted ice has to go somewhere.
Rapidly increasing sea levels could have drastic consequences for human populations, especially the hundreds of millions of people who live in coastal areas or on islands. Coastlines will erode, storm surges will rise, and some areas could become completely uninhabitable.
Here’s what Miami, Florida would look like after just a meter of sea level rise, according to a visualization created by Andrew David Thaler (@SFriedScientist), a marine science PhD and ocean-science website editor: