Sound Science Bite: April 12. Slowing Down the Thermal Conveyor Belt

On April 11 (2018) an article in the journal Nature, "Observed fingerprint of a weakening Atlantic Ocean overturning circulation", reports that the Atlantic meridional overturning circulation (AMOC) has weakened by 15% since about 1950, and the culprit appears to be increasing carbon dioxide in the atmosphere. You may recall the rather silly movie (IMHO), "The Day After Tomorrow", in which a new ice age was suddenly initiated by the failure of the AMOC. The AMOC involves cold, salty water in the vicinity of Greenland sinking and being replaced by warm water flowing northward from the southwest Atlantic, Caribbean, and Gulf of Mexico. The cold water flows deep under the ocean surface, past southern Africa, and reappears at the surface in the Pacific. Will this slowing of the AMOC initiate a new ice age as indicated by the movie?

If climate history is the guide, the likely answer is "no". After the last ice age melting ice led to the introduction of large amounts of fresh water into the North Atlantic, which led to an increased amount of sea ice in the winter. Winters in Europe became severely cold, but summers were not nearly as affected. The important point is that no new ice age was initiated. This is clearly an analogous situation, but differs in many respects, including the cause and the details of the cooling of the North Atlantic. My wager, based on the common factor of a cooling North Atlantic coupled with increased greenhouse gases, is on colder European winters and hotter summers.