Responses
I am merely a weather enthusiast rather than a meteorologist, so bear with me:
1. From what I have read, there are a number of factors that affect what the winter will be like. Whatever state ENSO is in is just one.
As an example, I remember reading in Fall 2002 how there was supposed to be an El Nino, so I figured that the area I was in at the time (south central Missouri) would have a mild winter. Instead, it was genuinely cold. As another example, the winter of 2022-23 had a La Nina, yet eastern Oklahoma (where I live) was a bit wetter than normal, even though it should have been warmer and drier than normal, based on how La Nina normally affects climate of this area. Meanwhile, this area has had a drier than normal winter this year, even with an El Nino that would normally raise the odds of having a wetter winter than normal. So, I think the most that can be said about whatever state ENSO is in is that it merely increases the probability of the winter being a certain way, rather than it definitely making the weather act one way or another.
2. From what the meteorologists who keep this blog have told me, a big reason why they are forecasting a La Nina to start later this year is because we had a strong El Nino this past winter, and because, whenever those happen, they are often followed by a La Nina. There is a chance that something else could happen, plus, from what the atmospheric scientists keeping this blog have written in the past, springtime tends to make forecasting future ENSO states harder. But, the historical record increases confidence in the forecast for La Nina to develop later this year.
3. I don't know anything about a connection between PDO and El Nino. So, would you explain this further?
4. It is true that the sun is the biggest driver of this planet's climate and weather. In fact, if it were not for the sun, Earth would literally not exist.
It is also true that there are other factors, such as the Moon, how long days last, the oceans, the continents and where they are, mountain ranges and plateaus and where they are, the fact that the Earth is tilted on its axis (as well as how it wobbles very slowly), and the atmosphere along with gases that compose it, among others.
That said, there are some atmospheric gases that store heat, two of which are water vapor and carbon dioxide. (This was discovered in the 19th century.) It was later learned that increasing concentrations of these gases would increase the temperature. And, since the age of industrialization began in the 19th century, human society has been burning fossil fuels (including oil and coal), which has resulted in continually adding carbon dioxide to the atmosphere. We are continuing to do so, so carbon dioxide concentrations continue to go up.
This has resulted in temperatures worldwide gradually increasing for over a century, which has affected climate worldwide in different ways. Here in eastern Oklahoma, for instance, summer has gradually gotten longer, and now routinely continues through most of September, when it used to end around Labor Day (even as recently as 20 years ago). Likewise, winter here has grown milder overall. In Korea, where I lived for 6 years, it has made summers hotter (to the point where they now regularly get the extreme summer humidity that is common in places like Hong Kong but which was rare in Korea 20 years ago). I have no doubt that it is affecting the Ohio Valley as well. There are many other effects of this, which NOAA's many highly qualified atmospheric scientists could tell you about, in detail.
Now, is human-caused global warming the only factor affecting the climate? Absolutely not: As I wrote above, there are a lot of others, plus climate change is never the sole factor affecting climate and weather. To put this another way, while it is a factor, it is not the factor.
So, as they wrote in this post, global warming was a factor in why this past winter was so warm, but it was not the only one.
Though I am merely a weather enthusiast, I have read a fair amount about weather and climate over the years, so I figured I would use it to address the points you brought up.