Researchers have studied the effect of dark pavement from roads and parking lots and from concrete buildings on the urban heat island effect (101). These surfaces absorb more solar radiation during the day than surrounding areas and at night radiate more IR into the sky (102). The result is substantially higher temperatures than surrounding areas. In some locations, weather for the city or urban area is created by this urban heat island effect (103). An example is Atlanta, GA, which spawns its own thunderstorms at night during summer months (104).

Deliberate large-scale attempts to alter local, regional or global climate by changing the surface albedo have not been made. However, the IPCC estimates that land clearing since 1750 may have decreased overall radiative forcing by 0.2 Wm-2 by increasing the reflectivity of the surface (55), noting that assigning any significant impact on the global climate is at present speculative (105).

Others have recently attributed much greater significance to these land use changes in trying to explain why temperatures for North America predicted by climate models are higher than the actual temperatures over the last 250-1000 years (106-108).

It is estimated that raising the albedo (whitening) of all of the 2500 square Km of pavement and roofs in the greater Los Angeles area (15% of the total urban surface area) by 7.5% along with planting 10 million trees (5% of the total urban area of 10,000 square Km) could reduce temperatures in that area by 5?F (109). This would greatly reduce the demand for electricity to power air conditioners as well as reduce the formation of ground level ozone that increases with increasing temperature.

An alternative to reducing absorbed solar radiation that has been proposed (110) is to reduce the emission of GHG absorbable IR radiation by covering the surface with a high emissivity/low absorptivity material such that all emissions are in the atmospheric window (i.e., the non absorbing wavelengths for the GHGs) for IR. No such material exists, however, and existing high emissivity materials are also highly absorptive and would have to be shielded from sunlight, precluding their use during daylight hours.