New research shows that warmer climates in earth’s past, even with the moderate warming allowed for by the Paris agreement, have corresponded with sea levels 20 to 30 feet higher than those of today, according to The Washington Post.
Greenhouse gases emitted from human activities have driven temperatures up by roughly one degree Celsius from preindustrial levels. The Paris Agreement aims to limit these increases to no more than 2 degrees, with an aspirational goal of no more than 1.5.
However, about 125,000 years ago similar temperatures melted a large portion of Antarctica’s ice sheet, leading to the higher sea levels. These new findings suggest that 2 degrees Celsius of temperature increase, if sustained for a long enough period of time, is enough to raise sea levels substantially.
The paper was published Wednesday in the journal Nature, and included research from scientists in Australia, Japan, New Zealand, Spain, and the UK.
The research focuses on the Wilkes Subglacial Basin of Antarctica. Though it hasn’t been studied extensively, it is larger than California and Texas combined, with the potential to cause 10 feet of sea level increase. Scientists believe it could recede quickly, since it arises from a sloped depression on the ocean floor instead of sitting on land.
The new research studied sediments on the nearby seafloor, and found that much of the Basin’s ice has melted during warmer periods of the planet’s history. During certain eras, sediments were deposited from the areas where the ice is currently, suggesting that there was no ice in the Wilkes Subglacial Basin in those periods, which also corresponded to periods that are known to have been much warmer, with higher sea levels. Yet, some of these eras were only slightly warmer than our own.
“It doesn’t need to be a very big warming, as long as it stays 2 degrees warmer for a sufficient time, this is the end game,” said Imperial College London geologist David Wilson, one of the authors of the Nature study. “We say 2 degrees beyond preindustrial, and we’re already beyond preindustrial. So this is potentially the kinds of temperatures we could see this century.”
However, the warmth was sustained over thousands of years in past eras, and the recent study was not able to assess how long it took for the ice to melt from the basin.
“We can’t necessarily say things didn’t happen quick, but we can’t resolve that in our data,” Wilson said.
The West Antarctic ice sheet is considered the most pressing risk for rising sea levels, and the US and UK governments are preparing a multiyear study on the Thwaites glacier there, which is already shedding 50 billion tons of ice each year. However, the new research suggests with just a little bit more warming, the much larger East Antarctic ice sheet might not be far behind.