Consider the following statements in respect of the Indian Ocean Dipole (IOD):

1. IOD is the difference between the temperature of the eastern (Bay of Bengal) and the western Indian Ocean (Arabian Sea). 

2. The IOD is an ocean-atmosphere interaction that is a much stronger system than El Nino.

3. El Nino is a cold ocean current along the coast of Peru as a temporary replacement for the warm Peruvian current.

4. A positive IOD event is developing at times of an El Nino, while a negative IOD is associated with La Nina.

How many of the statements given above is/are correct?