The Atlantic Multi-decadal Oscillation (AMO) has been found to affect climate for periods of 20 to 30 years. It has been linked to fewer Atlantic hurricanes, drier summers in Britain and Ireland as well as drought in northern Africa’s Sahel region.
The impending onset of the negative (cold) phase of the AMO can be predicted by a slowing of North Atlantic ocean currents, which has recently been observed.
The weaker currents fail to bring warmer waters that typically move from the tropics to the North Atlantic during the positive phase.
Writing in the journal Nature, lead researcher Gerard McCarthy says that since the new negative phase of the AMO could be a degree cooler, it may temporarily offset the effects of global warming in some areas.
The AMO has undergone three major transitions over the past 90 years. It brought significant warming during the 1930s and the mid-1990s, and cooling during the 1970s.