Energy from the Sun drives climate by heating Earth's surface unevenly. Ice also reflects incoming sunlight, cooling the poles even more. The temperature difference sets the ocean and atmosphere in motion as they work together to distribute heat around the planet. The Sun's energy is the primary driver of Earth's weather and climate systems. Unequal heating of Earth's surface produces large regions of rising and falling air, which trigger horizontal wind flow across Earth's surface and in the upper zone of the troposphere.