ENSO is the dominant source of interannual climate variability in the tropics and throughout the globe. Understanding ENSO's dynamics, predicting El Niño and La Niña, and anticipating changes in ENSO's characteristics and impacts are thus of vital importance for society. This session invites contributions regarding the dynamics of ENSO, including multi-scale interactions; paleo ENSO variability; ENSO impacts on climate, society and ecosystems; seasonal forecasting of ENSO; and climate change projections of ENSO. Studies aimed at understanding ENSO differences among coupled models are especially welcomed, including work related to the upcoming CMIP5 comparison.