The El Niño-Southern Oscillation (ENSO) drives many of the catastrophic climate events that occur from one year to the next: floods, droughts, wildfires, and hurricanes. 

However, climate scientists do not yet know how ENSO will respond to climate change. A new multi-century reconstruction of ENSO variability, based on fossil corals from Papua New Guinea, reveals a century-long decline in the number of El Niño events starting in the mid-1500s. It is the first time such a shift in activity has been documented in either modern observations or past reconstructions.

This reduced activity coincided with the initiation of an unusually cool period in the Northern Hemisphere called the Little Ice Age (LIA), which continued on into the mid-1800s.

The reconstruction gives scientists a better picture of how ENSO behaved during the coolest period in the last 1,000 years and provides a new baseline for natural ENSO variability to improve future climate change projections.

Paper: Kelly A. Hereid et al., GEOLOGY doi: 10.1130/G33510.1.