Reduction in albedo of the Earth's surface
Human activity has increased the extent to which solar energy is reflected back from the Earth, thus modifying the global radiation balance. This has been achieved by the destruction of forests and desertification. The planetary albedo is also altered by the introduction of aerosols and particles into the atmosphere.
It has been estimated that the reflection of solar radiation may have increased by 1 W per square metre over the whole of human history, and probably by 0.2 W per square metre over the last 30 years. It is estimated that over the next 100 years this may be increased by from 0.3 to 1 W per square metre. The expected proliferation of solar collectors would contribute to this effect.
Global energy change due to modifications to the planetary albedo are likely to be quite small compared to the expected radiative effects of trace gases and perhaps even to natural climatic variability.