its mostly human-caused but the environment does a little
There is a broad consensus among the experts that human activities are the primary cause of climate change.
Both, but mainly human caused.
If you believe in a 4 Billion year old earth, or even if you believe in a few thousand year old earth, you have to recognize the fact that the Ice age happened with no human intervention, just as the great thaw happened with no human intervention. Just because its getting hot or cold doesn't mean the world is ending, it means the world is changing. Weather happens, seasons change. Nature can take care of itself, and it has for billions/thousands of years. Stop blaming people for polar bears losing their natural habitat.