Answer:
1. increase
2. increase
If the carbon dioxide levels increase, global temperatures will increase, because carbon dioxide is a greenhouse gas.
If I chose stay the same, this is what would happen:
If the carbon dioxide levels stay the same, global temperatures will stay the same because not too much or less carbon dioxide is being emitted to the atmosphere.
If I chose decrease, this is what would happen:
If the carbon dioxide levels decrease, global temperatures will decrease because there will be less greenhouse gases to make the atmosphere warmer.
Hope this helped you!