I'm not Michelle but I can try and answer as best I can. I covered what the IPCC report says about ENSO here > https://www.climate.gov/news-features/blogs/enso/enso-and-climate-chang…

And basically, there have been some changes but it's too difficult to say if climate change is the cause.

But the IPCC report isn't doing any new science but discussing the totality of science already done. There are groups of scientists who claim (with peer reviewed research) that El Ninos will be come more likely. That is what I imagine Seth Bornstein is referring to.

About the only thing for certain is that a lot more research will produced looking at this problem.