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.
I guess nothing is going to convince me. I've heard a lot of evidence that cheating did take place. It just seems so handy that it keeps getting "proven" false.
There used to be a lot more lightning. I would photograph it, and had hundreds of pictures, pretty much every year. Not the last few years. People forget how different the pattern was in the '90s and early 00s. It's very ridgy now, jet stream north even at cooler times.