The temperature of the Earth’s atmosphere is, put simply, determined by three variables connected with solar radiation. The most important of these is incident short-wave solar radiation, which supplies the Earth with energy. The second is the reflection of this radiation by clouds, by particles in the Earth’s atmosphere or by ice in the polar regions. These immediately reflect part of the incident solar energy back into space. The third variable in the global heat budget is long-wave heat radiation. This arises when the land or ocean surface releases solar energy back into the atmosphere. Part of the long-wave heat radiation released by the planetary surface is absorbed by greenhouse gases and then re-emitted in all directions – including back downwards, causing the same radiation to heat the Earth again. So it is the long-wave radiation that causes the greenhouse effect. By contrast, almost all radiation management (RM) methods aim to increase the reflection of incident short-wave solar radiation.