  We begin by providing observational evidence that the probability of
encountering very high and very low annual tropical rainfall has increased
significantly in the recent decade (1998-present) as compared to the preceding
warming era (1979-1997). These changes over land and ocean are spatially
coherent and comprise of a rearrangement of very wet regions and a systematic
expansion of dry zones. While the increased likelihood of extremes is
consistent with a higher average temperature during the pause (as compared to
1979-1997), it is important to note that the periods considered are also
characterized by a transition from a relatively warm to cold phase of the El
Nino Southern Oscillation (ENSO). To further probe the relation between
contrasting phases of ENSO and extremes in accumulation, a similar comparison
is performed between 1960-1978 (another extended cold phase of ENSO) and the
aforementioned warming era. Though limited by land-only observations, in this
cold-to-warm transition, remarkably, a near-exact reversal of extremes is noted
both statistically and geographically. This is despite the average temperature
being higher in 1979-1997 as compared to 1960-1978. Taken together, we propose
that there is a fundamental mode of natural variability, involving the waxing
and waning of extremes in accumulation of global tropical rainfall with
different phases of ENSO.
