Climate change

James Hansen Says Greenland Melt May Cool North Atlantic

Icebergs drift by the mountains in Scoresbysund, Greenland. Inflows of cold, fresh water from Greenland would slow deep currents that carry cold water south, cooling the North Atlantic.

Bloomberg,

17 May, 2013

Greenland ice melting at an expanding pace may begin cooling the North Atlantic and increasing the severity of storms by 2075, said James Hansen, the former NASA scientist who raised concerns about global warming in the 1980s.

“If we stay on this path where the rate of mass loss from Greenland doubles every 10 years, we would get to a situation by about 2075 or 2080 where the mass loss is so fast that it causes the whole North Atlantic to be colder,” Hansen said in London.

The findings are from computer models using current rates of ice melt and will be detailed in a paper that Hansen plans to finish writing in the summer, he said yesterday in an interview.

Inflows of cold, fresh water from Greenland would slow deep currents that carry cold water south, cooling the North Atlantic as tropical waters get warmer, Hansen said. That would increase a “temperature gradient” that’s conducive to stronger storms.

“It could happen sooner” than 2075, Hansen said. “If you look at how fast the mass loss is increasing, it looks like the doubling time is between five and 10 years,” he said.

The findings add to research showing the system of Atlantic currents that channels the warm Gulf Stream to the northeast and moves colder, deeper waters south may slow this century because of climate change. Possible effects include cooler temperatures for Europe -- or a moderation of rising temperatures -- and higher sea levels in New York, past studies have found.

The United Nations Intergovernmental Panel on Climate Change will this year publish the first section of a four-part report of its first comprehensive review of the climate since 2007. A leaked draft in December said it’s “very likely” the Atlantic Meridional Overturning Circulation -- the system of currents in the ocean -- will weaken this century. It is “very unlikely” it will collapse completely, the report showed.