Interannual climate phenomena are those whose characteristic variability and recurrence operate on a year-to-year (multi-month to multi-year) timescale, such as ENSO (El Nino-Southern Oscillation, with a period of roughly 2-7 years) and the Indian Ocean Dipole (also operating on interannual timescales); the Indian Summer Monsoon itself is fundamentally an annual (seasonal) cycle phenomenon tied to the yearly march of solar heating, while the Madden-Julian Oscillation (MJO) is a distinctly intraseasonal phenomenon, with a much shorter characteristic period of about 30-60 days, and is therefore not classified as an interannual phenomenon.