Effects of volcanism on tropical variability

The effects of large tropical volcanic eruptions on Indo-Pacific tropical variability are investigated using 122 historical ensemble members from the Coupled Model Intercomparison Project 5. Radiative forcing due to volcanic aerosols in the stratosphere is found to increase the likelihood of a model climatic response that projects onto both the El Nino-Southern Oscillation and the Indian Ocean Dipole (IOD). Large eruptions are associated with co-occurring El Nino and positive IOD events in the ensemble means that peak 612 months after the volcanic forcing peaks, marking a significant increase in the likelihood of each event occurring in the Southern Hemisphere (SH) spring/summer post-eruption. There is also an ensemble mean La Nina-like response in the third SH summer post-eruption, which coincides with a significant increase in the likelihood of a La Nina occurring. Taken together with the initial cooling, this La Nina-like response may increase the persistence of the cool global average surface temperature anomaly after an eruption. (c) 2015. American Geophysical Union. All Rights Reserved.