Collapse of Atlantic Circulation Possible.

• Position: CLIMATE MODELS

The idea of climate change causing a major circulation pattern in the Atlantic Ocean to collapse with catastrophic effects has been the subject of doomsday thrillers in the movies but, in climate forecasts, it mostly is regarded as an extreme longshot. However, a paper based on analysis done at a group of research centers, including Scripps Institution of Oceanography at the University of California San Diego, shows that climate models drastically may be underestimating that possibility.

A bias in most climate models exaggerates the stability of the pattern, called the Atlantic meridional overturning circulation (AMOC), relative to modern climate observations. When researchers removed the bias, then re-ran simulations, the result prompted them to predict a collapse of the circulation at some point in the future, setting off large-scale cooling in the North Atlantic. The collapse would stop AMOC, which delivers warm surface water toward Greenland then sinks as it cools and flows back toward the equator closer to the seafloor.

"The significance of our study is to point out a systematic bias in current climate models that hinders a correct climate projection," says...