Decadal variability in the tropical Pacific (TPDV) is known to influence precipitation, floods, drought, agricultural production and extreme weather both within and well beyond the tropical Pacific. Despite the prominent impacts, we have very little understanding of how much of TPDV is distinct from the El Nino-Southern Oscillation (ENSO). Numerous mechanisms for DVTP have been proposed in the literature, including: i) oceanic and atmospheric exchanges between the Pacific extra-tropics and tropics; ii) Interbasin connectivity, whereby decadal SST changes in the Atlantic and Indian ocean can modulate the tropical Pacific climate; and iii) External forcing, which includes greenhouse gasses, volcanic forcing and anthropogenic aerosols. Although all of the above mechanisms have likely played some role in past changes, we currently have very little understanding of their relative importance. This session seeks submissions aimed at clarifying the dominant drivers of tropical Pacific decadal variations, and the relationship of TPDV with ENSO.