Introduction | The Sun | Energy | The Greenhouse Effect | What Affects Climate? | Climate Change?

When the Sun's Energy gets into the Atmosphere...

Have you ever worn a dark colored shirt on a warm sunny day? Your dark shirt will absorb more heat than your friend’s light colored shirt. That will make you warmer. On a larger scale, this happens in the Earth system as well. Forests, lakes, oceans, glaciers, deserts, and cities all absorb, reflect, and radiate heat differently.

Take a look at the picture of glaciers in the Himalayan Mountains. What color is the ice? Is that color light or dark? What color is the land? Is it lighter or darker? —Light colors reflect light back into space, while dark colors absorb heat, warming the Earth.

Albedo is the percentage of the Sun’s energy that is reflected back by a surface. The type of surface that sunlight first encounters is the most important factor that affects the warming or cooling of the planet. Light colored surfaces like ice have a high albedo, while dark colored surfaces tend to have a lower albedo. What would happen if the ice melted? Would Earth’s albedo be higher or lower? Would this cause Earth to become cooler or warmer?

While it might be quite warm in the countryside on a summer day, it can get unbearably hot in a nearby city! That’s because the buildings and pavement in cities absorb loads of sunlight, much more than the countryside. These cities are called “heat islands.” The countryside is also cooled by water evaporating from lakes and given off by the plants in forests and fields. Cities have fewer plants and bodies of water and so are not cooled very much by evaporation.