climbing vs ascension

climbing and ascension both are nouns.

Word	Noun	Adjective	Verb	Adverb
climbing	Yes	No	No	No
ascension	Yes	No	No	No

As nouns, ascension is a hypernym of climbing; that is, ascension is a word with a broader meaning than climbing:

climbing: an event that involves rising to a higher point (as in altitude or temperature or intensity etc.)
ascension: a movement upward; rise above the ground

Other hypernyms of climbing include ascent, rise, rising.

climbing (noun)	ascension (noun)
an event that involves rising to a higher point (as in altitude or temperature or intensity etc.)	the act of changing location in an upward direction
	a movement upward; rise above the ground
	(astronomy) the rising of a star above the horizon