On Ever-Thinner Ice


A report released yesterday by the National Research Council (NRC) cautions that “the uncertainties associated with passing tipping points in the climate system are dangerously large.” Dan Vergano puts it in context:

The new report differs from past ones in taking continued global warming as inevitable and looking for impacts on humanity and animals, not just geophysical and weather effects like melting glaciers or drought. “The report is a break from the past in that it includes abrupt changes in the environment that can result from even small, steady increases in temperature or other climate change effects,” says geoscientist Peter Clark of Oregon State University in Corvallis, who was not on the report panel. “I think that is an important point [that] the report is making.” …

In coming decades, the report forecasts a high risk of the disappearance of summertime Arctic sea ice—an abrupt climate change impact already under way—and extinctions in the ocean and on land.

Rapid ecological shifts that threaten farmland as well as wildlife across broad regions, such as tropical forests, are rated as a “moderate” risk. An abrupt slide of the vast West Antarctic Ice Sheet into the ocean would suddenly sink coasts worldwide under 10 to 13 feet (3 to 4 meters) of water. The report rates the risk of this calamity as “unknown” although probably low for this century. …

[P]aleoclimate expert Thomas M. Cronin of the U.S. Geological Survey office in Reston, Virginia, expressed caution about the report’s conclusion that abrupt climate change would likely drive coral extinctions in the ocean or wipe out species in tropical forests. In the latter case, he said, “it is hard to separate human effects, or the timescale of possible extinctions.” On the other hand, Cronin also suggested that the report underplays the threat of the Atlantic Ocean’s circulation disastrously halting, or the sudden release of large quantities of methane from warming Arctic permafrosts.

Recent Dish on climate change here, here, and here.