If you live on the coast and don’t know how to swim, you may want to invest in some lessons (well, maybe some for your grandkids)—because according to NASA, our sea levels are going to rise much more than previously predicted.
In 2013, the United Nations’ Intergovernmental Panel on Climate Change reported that sea levels could rise by as much as 38 inches by 2100—but the report didn’t take into account the melting of land ice. NASA is now warning that this estimate is probably too conservative.
“We have a different picture than we had in 2012 when the last IPCC assessment came out,” says Steve Nerem, an aerospace engineer at the University of Colorado, Boulder. “Sea levels are rising faster than they were 50 years ago, and it’s very likely to get worse in the future. The biggest uncertainty in predicting future sea level rises is determining how quickly the polar ice sheets will melt in response to warming.”
An incredible complexity
Unfortunately, scientists still don’t fully understand the complex dynamics involving melting, mainly because they are unsure how warmer water might melt ice sheets and glaciers from underneath. But they’re most definitely melting—Greenland’s Jakobshavn Glacier may have just calved its largest chunk of ice ever just a few days ago. If that entire glacier were to melt right now, global sea levels would rise by a foot.
However, according to Eric Rignot, a glaciologist at NASA’s Jet Propulsion Laboratory in Pasadena, California, that would only be the beginning. “We’re talking about 6 meters—18 feet—and higher of sea level rise. Sea level rise might rise half a meter [roughly 3.3 feet] per century, or several meters per century. We just don’t know.”
What we do know is what has happened in the past. According to a recent study out of Oregon State University and the University of Florida, the last time the Earth had the same level of carbon dioxide in the atmosphere was around three million years ago—when the ice sheets had shrunk, causing sea levels to rise to around 20 feet higher than today.
But it’s not just ice sheets and glaciers we need to be concerned about: The global rise in temperatures means that the same amount of water now takes up more space. According to NASA, oceans absorb around 90% of the heat from global warming—and when anything (solid, liquid, or gas) gets warmer, it expands.
So who should worry about this change? Cities should take special note, especially the eight of the top ten largest cities in the world that happen to be situated on the coast, like Tokyo and New York City. Without advanced protective measures, these cities could experience massive loss of life in the upcoming decades.
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Image credit: Thinkstock
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