climber vs ascender

climber and ascender both are nouns.

Word	Noun	Adjective	Verb	Adverb
climber	Yes	No	No	No
ascender	Yes	No	No	No

As nouns, ascender is a hypernym of climber; that is, ascender is a word with a broader meaning than climber:

climber (noun)	ascender (noun)
an iron spike attached to the shoe to prevent slipping on ice when walking or climbing	(printing) the part of tall lowercase letters that extends above the other lowercase letters
someone who climbs as a sport; especially someone who climbs mountains	a lowercase letter that has a part extending above other lowercase letters
someone seeking social prominence by obsequious behavior	someone who ascends
someone who ascends on foot
a vine or climbing plant that readily grows up a support or over other plants