Survey of Experts Suggest Sea Level Rise Could Exceed 1 Meter by 2100

If global emission were to go unchecked and continue to be strong, sea levels could exceed 1 meter by the end of the century, according to a new survey of leading sea-level experts.

Most of the experts involved in the new study expect sea levels to rise more than the current Intergovernmental Panel on Climate Change (IPCC) projections of 28-98 centimeters by 2100. Sixty-five percent of the experts survey said they believed sea levels would rise more than than the high end projects put forth by the IPCC, which suggests that the IPCC maximum estimates are conservative.

More than 50 percent of the experts said that if global emissions were to continue unmitigated, sea levels would rise by 1.5 meters or more by 2100, while 27 percent said levels would rise by 2 meters or more.

But with strong emission reduction strategies, global sea levels may only rise as much as 60 centimeters by 2100 and no more than 100 centimeters by 2030, the survey suggested.

"While the results for the scenario with climate mitigation suggest a good chance of limiting future sea-level rise to one meter, the high emissions scenario would threaten the survival of some coastal cities and low-lying islands," said Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research. "From a risk management perspective, projections of future sea-level rise are of major importance for coastal planning, and for weighing options of different levels of ambition in reducing greenhouse-gas emissions."

The researchers admit, however, that there are certainly challenges in sea level rise simulations because the processes that cause sea level rise are complex and lead to uncertainties in the data.

"It this therefore useful to know what the larger community of sea-level experts thinks, and we make this transparent to the public," said lead study author Benjamin Horton from the Institute of Marine and Coastal Sciences at Rutgers University in New Jersey. "We report the largest elicitation on future sea-level rise conducted from ninety objectively selected experts from 18 countries."

The experts were selected from a group of 90 scientists, all of whom had published extensive research on sea level rise within recent years.

By 2300, 58 percent of the experts surveyed said sea levels would rise by 4 meters or more in the worst-case scenario.

"Overall, the results for 2300 by the expert survey as well as the IPCC illustrate the risk that temperature increases from unmitigated emissions could commit coastal populations to a long-term, multi-meter sea-level rise," Rahmstorf said. "They do, however, illustrate also the potential for escaping such large sea-level rise through substantial reductions of emissions."

Rahmstorf and his colleagues study is published in Quaternary Science Reviews.