You may remember from your Alice Through The Looking Glass that as the Walrus and the Carpenter ambled tearfully along the beach, "the sun was shining on the sea, shining with all its might".
By doing so, the sun, as always, was providing the required energy to fuel the Earth's weather machine. The destructive force of the hurricane, the power of the waves and the sultry warmth of a southerly breeze are all, ultimately, the radiant energy of the sun appearing in a different guise.
Not all the energy directed by the sun in our direction is absorbed, however. Some of the radiation is reflected back to space and the fraction so affected is known as the Earth's albedo, its reflecting power. The word comes from the Latin albus, meaning "white" - a reference to the high reflecting power of a white surface.
The albedo varies from place to place depending on the texture of the landscape, the local composition of the atmosphere and the elevation of the sun.
Fresh snow, for example, as you might expect, reflects up to 90 per cent of any solar radiation reaching it. Clouds reflect 70 per cent to 80 per cent of the sun's energy, while green fields reflect only about 20 per cent.
Water, strangely enough, reflects very little - only 4 per cent to 5 per cent - unless the sun is very near the horizon, in which case reflection is almost total.
With normal amounts of cloud, snow and vegetation, the total albedo of the earth-atmosphere system is estimated to be 40 per cent. In other words, two-fifths of the sun's incident energy is reflected back into space, while the remaining three-fifths is absorbed by the planet and its surrounding layers of air.
These proportions are critical to the stability of the global climate. At present, the temperature of the Earth remains, on average, constant over the years: the energy absorbed is exactly balanced by that lost again to space in the form of long-wave radiation.
However, if the Earth's albedo was to change even slightly, this delicate balance would be upset. This is one of the factors which make it difficult for scientists to assess the possible impact of the enhanced "greenhouse" effect.
The areas around the north and south poles, for example, are covered by ice and snow and absorb very little solar energy. However, if circumstances were to change so that there was less ice and more greenery in the polar regions, more energy would be absorbed and there would be a gradual rise in global temperature.