Like Hays' Our Changing Climate (1977), this is a responsible examination of the variables that can affect the earth's climate. But in contrast to Hays' streamlined introduction this goes back to the formation of the earth and to the climates and life forms of its different geological periods--and, on the way, goes into both the climates of Venus and Mars and the different clues (from fossils and radiometric dating to the presence of snails in the soil) which help us ""uncover"" the earth's ancient climates. Gallant surveys several theories on the causes of climatic change--natural and manmade--and several schemes for controlling its course, concluding as does Hays that the risks of climatic engineering are too great and pointing out that any benefit to the manipulators is sure to be accompanied by harm to others. Gallant draws on a wide range of sources, but most heavily on Reid Bryson's views (Climates of Hunger, 1977) on past and likely cooling periods and their effects--among those in the offing, ""drought. . . , shorter growing seasons. . . , and more highly variable weather around the world."" A conscientious investigation for those who are willing to take the detours, make their own connections, and accept general uncertainty for an answer.