In 2008, Phil Klotzbach and Bill Gray published a paper in Journal of Climate discussing a newly-developed Atlantic Multi-Decadal Oscillation index that utilized a combination of two predictors: 1) Sea surface temperatures (SSTs) in the far North Atlantic from 50-60°N, 50-10°W and 2) sea level pressures (SLPs) in the North Atlantic from 0-50°N, 70-10°W. At present, the index is calculated by weighing the SST component as 60% of the index and the SLP component as the remaining 40%. All values are standardized using the 1981-2010 climatological average as a baseline. Real-time monthly values are calculated from the NCEP/NCAR Reanalysis and are typically updated by the 5th of the following month.
Standardized monthly values of the Klotzbach and Gray (2008) AMO index from 1950-present are listed below: