Rising sea levels have been mostly measured in inches in the past decades, but scientists said they could increase more than 20 feet in the future as global warming continues to melt ice sheets in Greenland and Antarctica.
The dire projections are based on a look back at the climate record, with scientists finding that increases of 20 feet have happened at least twice over the past 3 million years when temperatures were very similar to what they are today.
If similar increases were seen across the globe, that could put tens of millions of people living in coastal communities from New York to Miami to Bangkok at risk of storm surges and increased flooding. Even NASA is fearing its launch pads could be threatened by climate change.
Many of these coastal communities are already seeing increased flooding – and that is just from global sea levels rising around 8 inches since 1880. Records also indicate the rate of sea level rise has intensified since the 1990s.
“Studies have shown that both the Greenland and Antarctic ice sheets contributed significantly to this sea level rise above modern levels,” Anders Carlson, an Oregon State University glacial geologist and paleoclimatologist, and co-author on the study that was published Thursday in Science, said.
“Modern atmospheric carbon dioxide levels are today equivalent to those about 3 million years ago, when sea level was at least 6 meters higher because the ice sheets were greatly reduced,” he said. “It takes time for the warming to whittle down the ice sheets but it doesn’t take forever. There is evidence that we are likely seeing that transformation begin to take place now.”
Peter Clark, an Oregon State paleoclimatologist and another co-author of the study, said that because current carbon dioxide levels are as high as they were 3 million years ago, “we are already committed to a certain amount of sea level rise.”
“The ominous aspect to this is that CO2 levels are continuing to rise, so we are entering uncharted territory,” Clark said. “What is not as certain is the time frame, which is less well-constrained. We could be talking many centuries to a few millennia to see the full impact of melting ice sheets.”
The researchers, analyzing everything from fossilized coral to records of ice sheets to geophysical models on sea level response, concluded that sea levels rose 20 to 30 feet higher than present about 125,000 years ago, when global average temperature was 1.8 degrees higher than preindustrial levels, similar to today’s average. Sea level peaked somewhere between 20 and 40 feet above present during an earlier warm period about 400,000 years ago, when global average temperatures are estimated to have been about 1.8 to 3.6 degrees warmer than the preindustrial average (though that estimate is uncertain).
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