Interesting that Michael Mann, who coined the acronym AMO no longer considers the AMO a real oscillation. The new research on AMO by Mann appears to be meant to be somewhat provocative, which is OK as it spurred some discussion on Twitter. His peer-reviewed article is called “Absence of internal multidecadal and interdecadal oscillations in climate model simulations” and its takeaway is right in the title. Essentially, Mann et al are questioning whether the ~60 year oscillation (and perhaps faster cycles) in the AMO behave as an internal property of the Atlantic ocean or whether any cyclic variation is externally forced, which could also be by changes in aerosols as I recall he didn't rule out.