“效应”的原义是“物理的或化学的作用所产生的效果”，也可泛指“某个人物的言行或某种事物的发生和发展在社会上所引起的反应或效果”。英语的对应词是effect。自然界和人间社会存在各式各样的效应。其中“温室效应” (green-house effect)是我们最常见的一种大气保温效应，与地球变暖(global warming)有关。例如：

1. The term “greenhouse effect” has two common meanings. There is a natural greenhouse effect that keeps the Earth’s climate warm and habitable. There is also a man-made greenhouse effect, which is the enhancement of Earth’s natural greenhouse effect by the addition of greenhouse gases from the burning of fossil fuels (mainly petroleum, coal, and natural gas).

“温室效应”这个词有两个基本意思：一个是使地球气候保持温暖和适宜居住的自然温室效应;另一个是人为温室效应，即由于燃烧化石燃料(主要是石油、煤和天然气)造成温室气体增多而导致的地球自然温室效应增强。

2. Earth’s natural greenhouse effect is critical to supporting life. But human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causing global warming.

地球的自然温室效应对维持生命是至关紧要的，但是人类活动，主要是燃烧化石燃料和砍伐森林，已加剧了这种自然温室效应，引起全球变暖。

与我们生存环境密切相关的另一种自然效应是“城市热岛效应”(urban h