When there's a long record of climate, like the one from the coral, we can ask the question of whether recent warm conditions are unusual or part of a natural cycle.

Our study indicates that in addition to being responsible for some of the year-to-year changes in East African climate, ENSO may also set the pace for slower decadal changes.

Only when we have a long-term perspective can we say anything at all about long-term variability, especially decadal variability.