I can remember when I didn’t know about oscillations at all, but then we had a series of them. First of all we learnt the big one, the El Nino-Southern Oscillation. Then there was the Pacific Decadal Oscillation. And now we have the Madden-Julian Oscillation or the MJO. This is an eastward movement of cloud and rainfall coming from the equator over a cycle of 30 to 60 days, causing fluctuations in tropical weather.