“…Thus, much effort has gone into understanding the factors that cause variations in ENSO behavior. These include stochasticity or weather noise (e.g., Blanke et al, ; Eckert & Latif, ), chaos stemming from the deterministic nonlinear ocean‐atmosphere dynamical system and the annual cycle (e.g., Jin et al, ; Münnich et al, ; Neelin et al, ; Tziperman et al, ), as well as changes in the background climate state (e.g., Fedorov & Philander, ; Wang & An, ) and processes external to the tropical Pacific (e.g., Kajtar et al, ; Kucharski et al, ; Terray et al, ). Investigating these processes requires the use of climate models of a certain degree of complexity, such as a simple conceptual model (e.g., Jin, ; Suarez & Schopf, ), an intermediate complexity model (e.g., Zebiak & Cane, ), or a comprehensive general circulation model, depending on the extent to which particular processes need to be isolated and controlled.…”