chapter  4
17 Pages


A large fraction of the net radiation at the bottom of the atmosphere (Section 2.8) is absorbed by the oceans which cover about 71 per cent of the Earth’s surface, and that absorbed energy is mostly used in evaporating water. Some 6×1013

tonnes are evaporated from the land each year, but about six times as much from the oceans (Chapter 6). So evaporation is an important part of the movement of energy, the theme of this second part of the book.