Year-to-Year Variability

Year-to-year, or interannual, variability is the change in an ocean or atmospheric quantity from one year to the next, the band of variation between seasonal cycles and multidecadal trends. In the ocean it is dominated by modes such as the El Nino Southern Oscillation, which shifts Pacific sea-surface temperature, thermocline depth, and rainfall on a two-to-seven-year cycle, along with the North Atlantic Oscillation and the Indian Ocean Dipole. Distinguishing this natural variability from a forced climate trend requires records spanning several decades, which is why long observation networks and reanalyses matter. It sets the noise floor against which sea-level and sea-ice trends are detected.