Our junior observor begins to see how it might work......

"If the snow made the land colder," he thinks out loud, "then the storms would get bigger."

"Yes," says the storyteller, "that is exactly right. The snow makes the land colder. The dark color of ordinary land, without snow, soaks up heat from the sun. But snow is another matter. Snow is white and soaks up very little heat. Most of the Sun's rays, maybe as much as 80 percent, bounce off. When it snows the land can get very cold."

"Hey, I just got another idea," said the kid listener.
"The snow makes the land colder,
the land makes the storm bigger,
the bigger storm makes the land even colder,
and the storms just keep getting bigger, and bigger, and bigger."

Our patient listener had just discovered a law of nature. It is called feedback and it may be the most important of any of nature's laws. In the upper figure (1), snow has just fallen and sends colder air over the ocean to make a bigger storm, which in the middle figure (2) spreads more snow. The larger area of snow sends even colder air out over the ocean to make an even bigger storm in the lower figure (3). The process of (positive) feedback keeps making bigger storms, and spreading more snow.

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