You may not know it, but clouds help control temperatures on Earth. Droplets of water or ice particles suspended in clouds, as well as bits of dust and other particles floating in the air, called aerosols, reflect and absorb light and heat coming into and leaving our planet.

Cloudy Climate

Some kinds of clouds insulate Earth and keep it warm, while other kinds shade the planet and keep it cool.

High, thin cirrus clouds tend to trap heat emitted by Earth, warming the planet.

Low, thick cumulus clouds tend to shade and cool Earth by reflecting sunlight back into space.

Jet planes streaking across the sky spew water vapor from their exhaust, leaving thin, wispy clouds, called contrails, in their wake.

Airy Aerosols

Aerosols are tiny dust, soot and other particles that float in the atmosphere, where they tend to absorb, scatter, and reflect incoming sunlight, shading and cooling the ground below.

In 1991, Mount Pinatubo in the Philippines erupted, spewing some 15 billion kilograms (33 billion pounds) of aerosols—mostly sulfur dioxide molecules—into the atmosphere, where they shaded Earth for more than two years. As a result, Earth cooled an average of 0.3°C (0.54°F) over several months.