Greenhouse effect. Some of the sun's incoming energy is reflected by the earth's atmosphere.
Some is reflected by the earth's surface. The rest warms the earth producing infrared radiation,
some of which escapes into space, some of which is reflected back into the earth's atmosphere,
causing further heating. Available at Phototake

Nature and Scenic Images by Carol and Mike Werner.
The Great American West is available at Alamy, AGEfotostock and Pixtal.
Look for Nature at Phototake Visuals Unlimited and Alamy.