‘The ominous aspect to this is that CO2 levels are continuing to rise, so we are entering uncharted territory …’
FRISCO — It doesn’t take much global warming to raise sea level by 20 feet or more, climate researchers said in a new review study finding that global sea levels have risen at least six meters, or about 20 feet, above present levels on multiple occasions over the past three million years.
An increase of just 1 to 2 degrees Celsius in global mean temperatures is enough trigger a big meltdown of Greenland and Antarctic ice, which means that the world’s coastal areas are going to be swamped in the global warming era — it’s just a question of whether it will take a few hundred, or a few thousand years.
“Studies have shown that both the Greenland and Antarctic ice sheets contributed significantly to this sea level rise above modern levels,” said Anders Carlson, an Oregon State University glacial geologist and paleoclimatologist, who co-authored the new study appearing in Science.“Modern atmospheric carbon dioxide levels are today equivalent to those about three million years ago, when sea level was at least six meters higher because the ice sheets were greatly reduced.
“It takes time for the warming to whittle down the ice sheets,” said Carlson, who is in OSU’s College of Earth, Ocean and Atmospheric Sciences, “but it doesn’t take forever. There is evidence that we are likely seeing that transformation begin to take place now.”
Because CO2 levels are already as high as they were 3 million years ago, “We are already committed to a certain amount of sea level rise,” said OSU paleoclimatologist Peter Clark, who co-authored the paper.
“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.”
Twenty fee of sea level rise would be catastrophic for hundreds of millions of people living in coastal zones. Most of Florida is less than 50 feet above sea level, and places like New Orleans, Dhaka and Singapore would be swallowed up by the sea.
“The influence of rising oceans is even greater than the overall amount of sea level rise because of storm surge, erosion and inundation,” said Carlson, who studies the interaction of ice sheets, oceans and the climate system on centennial time scales. “The impact could be enormous.