Ship tracks reveal pollution's effects on clouds

Narration: Jefferson Beck

Transcript:

The Earth is a bright planet.

From space, we can see why..more than half of our world is covered with clouds at any one time.

Those white clouds reflect a lot of sunlight back to space, helping to keep our planet relatively cool. But a NASA satellite instrument called MODIS is showing us that humans can change our planet's brightness. 

The pollution we put into the atmosphere actually alters clouds. The best way to see this is to look for signs of pollution in areas that have otherwise clean air...like the North Pacific, near the Aleutian Islands.

In clean ocean air, water vapor condenses around salt particles and marine sulfate particles creating clouds. 

To the naked eye, the clouds in the North Pacific all look about the same. But MODIS' sensor reveals a different story.

Long, skinny trails of brighter clouds hidden within, as ships travel across the ocean, sulfate particles in their exhaust create more cloud drops that are smaller in size, resulting in even brighter clouds. And, on clear days, ships can actually create new clouds. Water vapor condenses around the particles of pollution, forming streamers of clouds as the ships travel on.

Could air pollution actually curb global warming by making our planet brighter and more reflective?

Scientists are studying the phenomenon, but say it will likely not significantly slow global warming. The heat-trapping effect greenhouse gases - many of which lurk in the same pollution - will most likely keep temperatures on the rise.