温 (wēn): Warm, lukewarm, gentle. Think of the temperature of a pleasant bath (温水, wēnshuǐ). It signifies warmth.
室 (shì): Room, chamber, house. You see this in words like 教室 (jiàoshì, classroom) or 办公室 (bàngōngshì, office).
效 (xiào): Effect, result, efficacy. A common word is 效果 (xiàoguǒ), meaning “result” or “effect.”
应 (yìng): Response, reaction. It often combines with other characters to describe a phenomenon, like in 反应 (fǎnyìng, reaction).
When combined, 温室 (wēnshì) literally means “warm room”—a perfect description of a greenhouse. 效应 (xiàoyìng) is a set phrase meaning “effect” or “syndrome.” Therefore, 温室效应 (wēnshì xiàoyìng) translates directly and perfectly to “greenhouse effect.”