It sometimes seems that there is a Wizard of Oz theme to many aspects of modern-day life. By clicking a computer mouse akin to Dorothy's heel taps, you can be whisked away to faraway places to vicariously experience wondrous sights through the technological eye of the Web. And the modern notion of a closely connected world doesn't end with the Internet. In a blink of a camera's eye, CNN beams television signals to communication satellites orbiting the earth, dispersing breaking news to the world.

Indeed, at times, it does seem like we live in a very small world. Yet, from other perspectives, continents seem worlds apart. Consider that a tourist in Australia can be sweltering in broiling heat while residents of Buffalo, NY dig out from two feet of snow. It is an irrefutable fact of life on this planet that while the Northern Hemisphere shivers in winter, the Southern Hemisphere simultaneously basks in summer. There are just some things that technology can't shorten or shrink.

Seasonally speaking, why are the hemispheres so far apart? What are the global controllers of temperature? Are there smaller-scale processes at work? To gain insights to the answers to these and several other fundamental questions, please click your heels to Color Plate 3.A.