Global Warming

Rough Waters Ahead: Climate Change Report Ups Sea-Level Projections

The latest international climate-change report has upped the expectations for rising sea levels as the globe warms — a change scientists anticipated thanks to an improved understanding of the potential contribution from melting ice sheets.

Six years ago, the Intergovernmental Panel on Climate Change's (IPCC) Assessment Report 4 (AR4) projected that sea levels would increase by as much as 1.9 feet (0.58 meters) by the end of this century. In a summary released Friday (Sept. 27), and in a draft unveiled today (Sept. 30), the latest report — the Assessment Report 5 (AR5) — projects sea level increases of as much as 3.2 feet (0.98 m) by 2100.

The primary reason for the increase is that the new report takes into account the potentially large contributions from the enormous ice sheets covering Greenland and Antarctica.

"Projections in previous reports did not account for things like the speed-up of glaciers, which carry ice from the ice sheets to the ocean, or the melting of glaciers that are in direct contact with the oceans," said Josh Willis, a climate scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who has been involved in drafting both the current and past IPCC reports. "Although today's projections are not perfect, they are a bit better than the ones from the last IPCC report (AR4)."