Observations of Atlantic SSTs show significant multi-decadal variability since 1870 (see red line in figure 2 below), often termed the Atlantic Multi-Decadal Oscillation (AMO), though there is no clear evidence that it is really an ‘oscillation’. There is discussion about whether this variability is due to external forcings or internal processes. Ting et al (2009) published Figure 1 below showing a range of GCM estimates of the AMO, suggesting that it is an internal fluctuation (like many other authors). Figure 2 is an estimate from HadCM3 using the raw output from the GCM rather than using the EOF methodology of Ting et al. Although the AMO is similar, there does appear to be a bit of a trend, and would be an outlier when compared to the other GCMs.