Study suggests that global sea level is less sensitive to high atmospheric carbon dioxide concentrations than previously thought.
From STANFORD’S SCHOOL OF EARTH, ENERGY & ENVIRONMENTAL SCIENCES
Ice sheets may be more resilient than thought, say Stanford scientists
But there may be some good news amid the worry. Sea levels may not rise as high as assumed.
To predict sea level changes, scientists look to Earth’s distant past, when climate conditions were similar to today, and investigate how the planet’s ice sheets responded then to warmer temperatures brought on by increased carbon dioxide in the atmosphere.
In a recently published study in the journal Geology, PhD students Matthew Winnick and Jeremy Caves at Stanford School of Earth, Energy & Environmental Sciences explored these very old conditions and found that sea level might not have risen as much as previously thought – and thus may not rise as fast as predicted now.
To better understand global sea level rise, Winnick and Caves analyzed the middle Pliocene warm period, the last time in Earth’s history, approximately 3 million years ago, when carbon dioxide levels in the atmosphere were close to their present values (350-450 parts per million).
“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,” said Winnick.
These similarities are why the Intergovernmental Panel on Climate Change (IPCC), the group responsible for global sea level rise projections, focuses on the mid-Pliocene warm period to inform their computer models.
Previous studies of the mid-Pliocene warm period used oxygen isotope records to determine the volume of Earth’s ice sheets and, by proxy, sea level. Effectively, the oxygen isotope records act as a fingerprint of Earth’s ice sheets. By combining the fingerprint with models of ice sheet meltwater, many previous researchers thought that sea level was likely 82 to 98 feet (25 to 30 meters) higher during the Pliocene.