So if the oceanic circulation looks like this:
And the resulting 2500m (deep) ocean age looks tile this:
Why should a PDO index that basically describes which side of the Pacific Ocean the ancient deep water is upwelling on track with or even lead global surface temperature? Why would global temperature care which side of the Pacific the cold water emerged on? And it isn’t just PDO. Everyone is gaga about El Nino and global temperature. Same problem. Why?
El Nino’s are in some sense junior PDO’s and MJO’s are similarly mini El Ninos. My current hypothesis is that they are all part of some homeostatic global thermoregulatory mechanism. Now, how to test this?