This meant he was now very high up

What does “this meant he was now very high up” refer to? Does it refer to the “strange, icy winds” alone or does it refer to the whole of the previous explanations {more trees, colder air, icy winds}?

“After all,” said Shasta, “this road is bound to get somewhere.”
But that all depends on what you mean by somewhere. The road kept on getting to somewhere in the sense that it got to more and more trees, all dark and dripping, and to colder and colder air. And strange, icy winds kept blowing the mist past him though they never blew it away. If he had been used to mountain country he would have realized that this meant he was now very high up— perhaps right at the top of the pass. But Shasta knew nothing about mountains.


It essentially refers to all the small changes associated with ascent.