Differences in solar energy cause temperature differences. Since warm air rises and cold air sinks, these temperature differences create pressure differences as well. And these pressure differences create wind patterns which are a key feature of Earth's climate.

Warm, rising air and cool, sinking air create these convection cells. At 30° latitude (both north and south), the equatorial air has cooled and sinks, creating a high pressure zone and pushing the surface air away to the north or south.

At 60° latitude (both north and south), cold polar air meets warm air from the south. Since the warm air is less dense, it is deflected upward toward the pole, where it cools and sinks again, creating high pressure at the poles.

These convection cells greatly affect climate:

• Warm air can hold more moisture than cold air, so it is generally more humid
• Low pressure areas are relatively wet and stormy, while high pressure areas are frequently cloudless

Look at a satellite photograph to see these phenomena in action:

Wet weather (dark area) is common along the equator, where many rainforests are found. And clear, dry skies are common between 25° and 35° degrees north and south latitude—just where deserts are often located! Convection cells are an important cause of both.

Solar energy fuels climate, but it's not the only factor. What else affects climate?