lowering vs decrease

lowering and decrease both are nouns.

Word	Noun	Adjective	Verb	Adverb
lowering	Yes	Yes	No	No
decrease	Yes	No	Yes	No

As nouns, decrease is a hypernym of lowering; that is, decrease is a word with a broader meaning than lowering:

Other hypernyms of lowering include diminution, reduction, step-down.

lowering (noun)	decrease (noun)
the act of causing to become less	the act of decreasing or reducing something
the act of causing something to move to a lower level	the amount by which something decreases
	a change downward
	a process of becoming smaller or shorter

lowering (adjective)	decrease (adjective)
darkened by clouds

lowering (verb)	decrease (verb)
	decrease in size, extent, or range
	make become smaller