Answer to Question 1
Answer: It was a treaty signed by all the major nations of the world except the United States. Its purpose was to cut greenhouse gas emissions by an average of 5 percent below 1990 levels. It is due to expire and not yet been replaced.
Answer to Question 2
Answer: Feedback mechanisms are numerous in all sorts of places in the Earth's subsystems. The student answer here should explain that a feedback is a natural reaction to change in the status of a system. Most feedbacks are negative feedbacks, therefore tending to dampen the swing of the subsystem away from equilibrium. However, some are positive. The student should illustrate feedback mechanisms with an example (e.g., the disappearance of ice that would decrease albedo).
