bidecadal
Every 200 years
Every 100 years is called a century, made up of 10 decades.
True.
The letter "Y."
An event that occurs once every three years.
it is a a centry
People born on a double leap year
Biennial (biannual is twice a yesr)
Quinquennial -Definition of QUINQUENNIAL. 1: consisting of or lasting for five years . 2: occurring or being done every five years - quinquennial noun - quin·quen·ni·al·ly ..
El Nino.
Eventual world climate change
Eventual world climate change
When used as an adjective, it means occurring every, or last for, four years. As a noun, it references an event that occurs every four years. (see: http://dictionary.reference.com/browse/quadrennially )
Biannual can be used in a sentence as an adjective to denote an event that occurs twice a year, or every two years. So, "It's a biannual event" is a rather ambiguous statement.
Every 4 years
An example of an occasional climate event that occurs every 3-8 years is the El Niño Southern Oscillation (ENSO). It is a climate pattern that involves the periodic warming of sea surface temperatures in the central and eastern tropical Pacific Ocean, leading to significant impacts on weather patterns worldwide.