Climbing is a want, but it satisfies needs for happiness, challenge, exercise, nature, fraternity, etc. The goal in a relationship is not to compromise on needs but to find solutions that satisfy both needs. Communication is the hardest part, and it can require peeling several outer layers of issues and feelings to discover the underlying needs.
Also, the tactic of "If I'm climbing too much, tell me" (basically asking your SO to manage you, which is quite a responsibility -- an impossible line between not getting enough and being a nag) does not work. (I think Chuck mentioned something like this on page 1.)