Global warming theory just isn't that complicated, nor is it hard to explain. An enhanced greenhouse effect causes the lower atmosphere to warm, due to an energy imbalance (less IR radiation being lost than solar energy being absorbed) until the emitted IR radiation once again equals the amount of absorbed sunlight. The theory is the Earth must increase its temperature until global energy balance is once again restored. This is the most basic global warming theory, as NOAA, NASA and many other scientific bodies explain.
There may be people who would argue against that, but they aren't posting here.
Calculations based on experiments and theory predict the amount of warming directly caused by the extra CO2 is, by itself, relatively weak. It has been calculated theoretically that, if there are no other changes in the climate system, a doubling of the atmospheric CO2 concentration would cause about 1 deg. F increase, in the global average We may be about 50% of the way toward a doubling of atmospheric CO2, due to fossil fuel burning, burning forests and turning them into parking lots, cities, pastures, cropland or highways and deserts.
The unknown, and very contentious predictions of what that small increase will cause, that is where the major conflicts seem to be.
The theory also predicts (and the models use theory to try and predict these changes) a certain kind of change, different than if the sun was causing warming, or if water vapor was increasing, or if ocean circulation was causing warming.
All of this is basic theory, and when measurements showed this kind of warming, what is predicted by theory, it was considered validation of the theory.
As Cohen et al 2014 states plainly, the theory does not predict winter cooling. There isn't currently any theoretical model that creates a scenario where boreal cold season cools, while the boreal warm season warms.
Why it's happening is of great interest to climate science.
Is it a natural cycle? Or is it due to greenhouse forcing, and an unexpected negative feedback? Is it due to early snow, due to the warming boreal summers?
Is it a change to the jet stream flow?
Why is the Pacific cooling? Will this pattern continue? These are scientific issues.
Ignoring, or worse, rejecting the consensus about global warming theory is the last thing I expected here.
But there is little doubt now, explained or not, that the drastic and long term cooling trend for the boreal cold season is happening, and that it does not fit with current global warming theory.
This does not, as some assume, mean that increased greenhouse forcing will not happen. It does mean that mother nature, as always, laughs at mankinds hubris.
.
!