NVIRONMENTAL SUSTAINABILITY 2 questions

There are two quesions that need to be answered and each answer should be in 2 pages .
1st :
What factors other than human activities can contribute to global warming? Why is there a debate in the world today on whether human activities are solely responsible for global warming? What do you think? Please justify your answer through research and demonstrating logical reasons for your argument.
2nd:
Please discuss the various ways in which we can increase the supply of water in order to resolve the oncoming shortage of water fit for human use on Earth. Please demonstrate your own understanding of issues relating to this subject using research, examples and diagrams when writing the answer.

Thank you for the understanding.