A little while back, I posted how the PDO had a unusually high correlation with EPO in October (-PDO favors +EPO). It was a 75% correlation, going back to 1948. Now LR models are developing a +EPO for at least early October (this is a cold H5 anomaly vs the central pacific warmth of -pdo).
I don't know if it's from car emissions, but my money is on it continuing at least through my lifetime.. It seems to me to be something that has happened, and everything is catching up.