Albedo and temperature

Light that is not reflected is absorbed. We make use of this fact. In cold weather we often wear dark clothes, hoping they will absorb such heat as the Sun delivers, and in hot weather we wear light-colored clothes to reflect heat. Winter clothes are also thicker, of course, and we wear more layers of them, and summer clothes are thinner and we wear fewer layers. That is really why winter clothes are warm and summer clothes keep us cool, but the albedo of the clothes contributes to the effect. The difference is between approximately 0.10 for dark winter clothes and 0.90 for light summer clothes.

You can measure the difference more precisely by placing two containers of similar size—empty ice cream tubs are ideal—outdoors on a sunny day. Fill both containers with water at the same temperature and cover one container with a sheet of white card and the other with a sheet of black card. If you can bury both containers so their rims are at ground level, as shown in the diagram, your result will be more accurate. Leave them for about an hour and then measure the temperature of the water in each container, and you should find that the water beneath the black card is significantly warmer than the water beneath the white card.

Since the shade of the surface determines how much sunlight is absorbed, clearly albedo has an important influence on climate. Subtropical deserts would be even hotter than they are if they did not reflect more than 25 percent of the radiant heat falling on them. Antarctica and Greenland would be warmer if they were a darker color and absorbed more heat.

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