Earths Albedo and Net TOA Solar Radiation

The earth's planetary albedo depends mostly on cloudiness, but also on land use. There is no scientific theory to indicate that the planetary albedo has been and will remain constant, and a change of 1% in its value can have a large impact on the earth's climate system [8]. Accurate measurements of the albedo began in the 1980s. Satellite observations made continuously during the past twenty years indicate that it is relatively constant at 29 ± 2% [9,10]. These measurements are close to previous estimates of 30 [11] and 31% [12]. However, analyses of earthshine measurements suggest that it may have changed by as much as 5% during the past 15 a [13 15]. The earthshine measurements have met with some criticism [9], but they are based on sound theory. In the future, if additional sites are added to the earthshine observation network, these measurements may gain more acceptance and the differences between the earthshine and satellite measurements will have to be resolved. Taking the current earth albedo to be 29%, the net solar input into the planet is about 243 Wm 2 [16].

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