In a way that decreases or declines by degrees; in a manner showing gradual reduction.
From degressive + -ly (adverb suffix). The adverb form describes how an action or process occurs in a declining manner.
Technical language like 'degressively reduce emissions' sounds scientific and serious, but plain English ('gradually reduce') usually communicates better—jargon often obscures rather than clarifies.
Complete word intelligence in one call. Free tier — 50 lookups/day.