
You knew roaming freighters and oil tankers made waves, but…clouds? It’s true. Large ships are not a
significant source of pollution, but they spray a mist of sulfur dioxide into the air in the exhaust from their
smokestacks. The particles float into the atmosphere, creating peculiar cloud formations that carry more water
than ordinary clouds. They may also be less likely than the garden-variety clump of cumulus clouds to make
rain.
Because scientists don’t fully understand the role clouds play in global climate, understanding how they are
formed and shaped is a burgeoning area of study. In recent years, researchers have been most interested to
know how human activities -- on air, land and sea -- change natural patterns.
This image of clouds hovering over the northern Pacific was captured in 2002 by the Moderate-resolution
Imaging Spectradiometer (MODIS) aboard NASA’s Terra satellite.
NASA