In 500 years, sea levels could be more than 15 meters (50 feet!) higher than current levels. That’s according to a new study published this week in the journal Nature. They base this on greenhouse gas emission scenarios fed into computer model simulations to interpret sea level estimates. They also say that by the year 2100, we could have a 1.5 meter (nearly 5 feet) rise in sea levels. How were they able to reach these dire conclusions? By utilizing mechanisms previously discounted by other studies.
The study’s lead author is Professor Robert DeConto of the University of Massachusetts, and Dr David Pollard of Pennsylvania State University contributed as well. They note that previous estimates of global sea level rise may have “underestimated the problem by half because they failed to incorporate the full effects of factors including the break-up of ice sheets.”
Not only do their results run counter to what the Intergovernmental Panel on Climate Change (IPCC) has previously predicted, but they say their new study is a stark warning to coastal communities and low lying areas. Over the past 100 years, the global average sea level rise ranges between 0.8 to 3.3 mm per year, with an average rate of 1.8 mm per year. The IPCC’s last assessment report projected a worst-case scenario of 1 meter (3.2 feet) by 2100, and under a lower emissions scenario a rise of .28-.6 meters by 2100.
This new study “focused on the boundary between the ice and the seas – namely glaciers and ice sheets in Antarctica and Greenland.” DeConto and Pollard showed that the “instability of ice sheets and ice cliffs could be an important contributor to past and future ice retreat, leading to creeping sea levels.” The new study is twice as high as previous guesstimates,
They also predict that Antarctica alone could contribute more than one meter of sea-level rise by the year 2100, and greater than 50ft (15 meters) by 2500 if atmospheric emissions continue unabated. The study’s authors focused largely on West Antarctica and Greenland, with the former sitting on an geologically active fault zone. Part of West Antarctica is melting from beneath from warm water heated by tectonic pressure, magma, and friction. This area of the continent is home to some of the world’s largest volcanoes (see photo), though many are covered in snow and don’t have the uniformly accepted appearance of a lava-spewing caldera.
NASA has already concluded that despite all this, Antarctica is actually gaining ice due to heavy snowfall that never melts, thereby slowing sea level rise. Sea levels also vary depending on where you are located due to thermal expansion. The paper says that “research has focused on the role of the ocean, melting floating ice shelves from below. It is often overlooked that the major ice shelves in the Ross and Weddell Seas are also vulnerable to atmospheric warming.”
Ice sheets already floating on water that melt do not add to increased sea level rise as the ice shelves are already displacing the water beneath it. The study argues that if these ice sheets melt from atmospheric influences, it would allow land ice to melt further and end up in the oceans. If the current rate of sea level was at the top tier of 3.3 mm per year, that would equate to 84 inches by 2100. Current sea level rise are measured via the Jason-1, Jason-2, and TOPEX/Poseidon satellites, as well as tidal gauges located across the world.
“Although the future sea-level contribution in our model is greater than previously thought, it is based on credible mechanisms and is consistent with geologic evidence of past sea-level rise,” said Pollard. “We regard the results as worst-case envelopes of possible future behavior, and the mechanisms should be considered seriously in future work.” In other words, it’s not likely to occur but keep it mind.
In 2003, the late Michael Crichton gave a speech in which he said, “Let’s think back to people in 1900 in, say, New York. If they worried about people in 2000, what would they worry about? …
“Remember, people in 1900 didn’t know…what a radio was, or an airport, or a movie, or a television, or a computer, or a cell phone, or a jet, an antibiotic, a rocket, a satellite, an MRI, ICU, IUD, IBM, IRA, ERA, EEG, EPA, IRS, DOD, PCP, HTML, internet. interferon, instant replay, remote sensing, remote control, speed dialing, gene therapy, gene splicing, genes, spot welding, heat-seeking, bipolar, Prozac, leotards, lap dancing, email, tape recorder, CDs, airbags, plastic explosive, plastic, robots, cars, liposuction, transduction, superconduction, dish antennas, step aerobics, smoothies, twelve-step, ultrasound, nylon, rayon, Teflon, fiber optics, carpal tunnel, laser surgery, laparoscopy, corneal transplant, kidney transplant, AIDS… None of this would have meant anything to a person in the year 1900. They wouldn’t know what you are talking about.
“Now. You tell me you can predict the world of 2100. Tell me it’s even worth thinking about. Our models just carry the present into the future. They’re bound to be wrong. Everybody who gives a moment’s thought knows it.”