Once again, the scientific basis of the argument is handwaved aside, which is a curious thing. Maybe another look at the facts will help. (haha, just kidding, facts are the last thing that will matter in a debate)
Theory states that all things being the same, greenhouse forcing will cause the most warming in winter, in the northern hemisphere, at high latitudes… This is why the IPCC and others predicted (later called projections) milder winters, more rain, less snow, fewer extreme cold events, and both animal and plant life moving northward, in response to the warming.
You can see this sort of warming looking at the 25 year trend here. If the next 25 years looked the same, it would be evidence of greenhouse warming, what is called global warming, mainly from an increase in CO2. Nobody familiar with the science would bat an eye, if the trend continued, that would be global warming. The theory is confirmed.
Looking at what did happen, the 25 year trend clearly shows the warming not only did not continue, there was significant cooling of the very areas where warming was expected to be the greatest.
Now normally this would be a problem for the theory, since there has been enough time to say it’s significant, and the evidence shows what was expected did not happen. There were no large volcanoes to cause it, and air pollution from China has been ruled out as the cause. But that’s not what has happened.
The claims are many about what has happened, but of course none of them challenge the theory. They are too numerous to list, but they fall into several categories, the main three being simple enough.
First, it didn’t happen. Some actually claim the warming has continued, and for various reasons the GISS data is wrong, incomplete, or something, in any case, it doesn’t show what happened, and the warming continued just aspredicted.
Second, it happened, but it’s due to either heat being buried, ocean patterns, or something else. This at least deals with the measurements, which clearly show the warming did not occur as predicted.
Third, it’s actually blamed on global warming. While this sounds insane, it’s actually a possibility, that greenhouse forcing has caused changes that actually lead to colder winters for large portions of the northern hemisphere.
While the third option is most scientific, it’s also the hardest to embrace, because if THAT hypothesis is true, there is no doubt the global warming theory is completely wrong. Not that the greenhouse effect is wrong, but the theoretical results of greenhouse forcing are not happening. Even worse, the opposite is happening/
Why does this matter to the topic at hand?
Because if the cooling is due to global warming, it confirms global warming.
If the winters had warmed, that would confirm global warming.
At which point the theory is impossible to falsify, it predicts everything. Which means it predicts nothing.
Which is of course, why so many firmly insist the 25 year trend shown in the GISS graphic can’t be happening, or it means nothing, or it’s cherry picking, anything to avoid the unpleasant thought that maybe there is a problem here.
If the thirty year trend (in 5 years time) shows a continued cooling, then there is going to be some real concern, not because the theory was so wrong, but over what, if anything, we can do about it. The predictions and projections of warmer winters didn’t alarm many people, they still don’t.
But if global warming is actually causing the trend, it is going to become a serious threat to life and property.
All irony aside, if Cohen et al 2012 and 2014 is actually right, things are going to get ugly. Warming can be ignored for the most part, but cold can’t be ignored, it’s too deadly, too disastrous to modern life.