Why does a small percentage of the country's population live in China's West?

Due to unfavorable climate and soil for farming and production, Western China is not conducive to living. Due to this, China's western regions are sparsely populated compared to other parts of China, where production and farming are more conducive.

The eastern, coastal provinces are much more densely populated than the western interior because of the historical access to water.

it is very hard for the climatologists to precisely predict how will the global temperatures be changing so there's lots of models, some of which differ significantly, this is due to multiple factors, and probably the most important is the human activity.

humans have been a key factor in climate change around the globe since the start of the industrial revolution, and in the past few decades the consequences are becoming more obvious. there's lots of emission of pollutants in the atmosphere as well as changing the environment on the surface itself, so it's really hard to predict how will that go in the future because there's some countries that are reducing the damage and are going towards green energy, while others are stubbornly continuing with pollution and damages to the environment.