Decadal time scales refer to a period of 10 years. In scientific contexts, it is often used in reference to climate patterns and weather systems that have an average duration of about ten years or more. This can include phenomena such as El Niño-Southern Oscillation (ENSO) cycles, which occur roughly every two to seven years but have a longer term average of around 2-7 decades. Decadal time scales are also used in reference to social and economic trends that tend to repeat themselves over periods of about ten years or more.