Sea Levels Might Not Rise as Fast as Previously Estimated, Researchers Say

It turns out that sea levels might not rise as high as previously estimated. Stanford researchers discovered this after taking another look at climate conditions long ago, in the middle Pliocene era, and how those conditions combined with concentrations of atmospheric carbon dioxide. They found that sea levels then--3 million years ago--might not have risen quite as much as thought, and therefore might not rise as much in the near future.

"The Pliocene is an important analogue for today's planet, not only because of the related greenhouse gas concentrations, but because the continents were roughly where they are today, meaning ocean and climate circulation patterns are comparable," Matthew Winnick, a Ph.D. student at Stanford, said in a news release.

Scientists often use Earth's past as a determiner for future forecasts. Winnick chose to examine the Pliocene because it was the last time in Earth's history when atmospheric carbon dioxide levels were similar to present concentrations. The Intergovernmental Panel on Climate Change (IPCC) also uses this time period for their sea level rise computer models.

According to the release, precious studies using oxygen isotope records estimated that Pliocene sea levels were between 82 and 98 feet higher. Today, these levels would require melting of the entire Greenland Ice Sheet and the West Antarctic Ice Sheet, along with roughly 30 percent of East Antarctic Ice Sheet. This amount of sea level rise would cover New York City in 50 feet of water.

Winnick worked alongside his fellow Ph.D. student Jeremy Caves at Stanford School of Earth, Energy and Environmental Sciences. Together, the researchers questioned these previous estimations, since they were based on the assumption that Pliocene ice had the same isotopic concentrations as today. The researchers decided to recalculate Pliocene seal levels and found that they were only 30 to 44 feet higher. However, Winnick cautioned that this is still enough to cover Miami, New Orleans and New York City, and threaten areas of San Francisco.

"Our results are tentatively good news," Winnick explained in the release. "They suggest that global sea level is less sensitive to high atmospheric carbon dioxide concentrations than previously thought. In particular, we argue that this is due to the stability of the East Antarctic Ice Sheet, which might be more resilient than previous studies have suggested."

This helps researchers better understand the Pliocene, but is still not a direct reflection of what the future of sea level rise holds, especially because we are increasing carbon dioxide at a much faster rate today, the release noted.

Their findings were published in the journal Geology. 

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