Is a reversal of AMO imminent

 

Whether the Atlantic Multidecadal Oscillation (AMO)—also referred to as Atlantic Multidecadal Variability (AMV)—is due to flip from its current warm phase to a cool phase is one of the most heavily debated topics in modern climatology.

Because the AMO operates on long timescales, a shift is statistically "due" soon, but an increase in Global temperaturea is making predicting the exact timing highly complex.

​Historical Timing Between Phases:

​Based on historical instrumental records, a full AMO cycle spans roughly 60 to 80 years, meaning each individual warm or cool phase typically lasts between 30 and 40 years. 

Historical phases of the AMO - warm/cool

As shown in the historical data above, the shifts follow a distinct multidecadal rhythm:

1880–1900: Warm Phase (~20 years                           recorded)

1900–1930: Cool Phase (~30 years)  

1930–1965: Warm Phase (~35 years)  

1965–1995: Cool Phase (~30 years)  

1995–Present: Warm Phase (Currently at              31 years)

Because the current warm phase has been active since roughly 1995, the North Atlantic has spent over three decades in a warm state. Statistically, this puts the climate system near the typical window for a reversal.

Likelihood of a Reversal:

​Predicting the likelihood of an imminent flip involves tracking two competing forces: internal ocean dynamics and external atmospheric forcing.

1. Signs of Potential Cooling (The Case for a Flip)

​Oceanographers closely monitor the Atlantic Meridional Overturning Circulation (AMOC)—the deep ocean conveyor belt that pumps warm water north. Subsurface observations in the North Atlantic subpolar gyre have periodically shown cooling trends and a weakening AMOC. When the AMOC slows down, it delivers less heat northward, which is historically the primary trigger for a negative (cool) AMO phase. Some decadal forecasting models suggest a transition toward a cooler North Atlantic state could materialize within the coming decade.

Even if the internal ocean circulation shifts to a cooling mode, it may manifest as a "pause" or a deceleration in rapid warming rather than a dramatic drop into historical cold anomalies.

Summary: While a shift toward the cooler ocean mechanisms of a negative AMO is moderately likely to build momentum over the next decade due to natural internal cycles, background global SST's warming may blunt or mask the actual cooling effects traditionally associated with past negative phases.

Written on the 2nd July 2026

Author - David I Birch 

Reference - Wikipedia - NCAR climate data -                        guide, NOAA GFDL.